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I've had some more time to think about certain things that bother me about the Thousand Sons as an army, and so this is a revised look at rebalancing them in a way to add more variety and options.

==Psychic Powers==

Tzeentch's Firestorm:Tzeentch's Firestorm is a ML 1 Witchfire with the following profile: Range 18, Strength 5, AP 3, Assault 1, Blast, Warpflame, Inferno: Inferno: A model that the hole of the blast is centered over takes a single S9 AP 2 hits instead of a single S5 AP 3 hit. This is basically the Librarius/Primaris, with the option to get a Lascannon Hit on the "Center" target in exchange for risking granting Warpflame. Fluffwise, the power is written up as "a storm of pink and blue fire" and this made sense also.

Boon of Mutation: Remove the Strength 4 hit from the ability. When you roll for a Chaos Boon, you may re-roll one die or the other.

Siphon Magic: Siphon Magic is a WC 2 Blessing that targets the Psyker. If cast successfully, the Psyker's unit gains +1 Strength until the start of the 1k Sons' next Psychic Phase, and the 1k Sons player immediately gains D3+1 Warp Charge; additionally, the Psyker and his unit gain +1 Strength until the start of the next Psychic Phase.

-Add restrictions to Treason of Tzeentch or other mind-control powers to prevent them from hitting the same unit multiple times in the same Psychic Phase. No stacking with Shroud of Deceit!

=Warlord Traits=

Forbidden Lore: Append the following: If your Warlord was not a Psyker, your Warlord is now treated as a Mastery Level 1 Psyker that must generate a power from the Lore of Tzeentch.

==Wargear==

Warpflamer Weapons: Are equivalent to weapons of their normal type, but with +1 Strength, and Warpflame. This means a Warpflamer is S5 AP 5, a Heavy Warpflamer is S6, AP 4, etc.

Icon of Flame: The simple tweak would be to replace "Soul Blaze" with "+1 Strength & Warpflame", for S5 Inferno Boltguns, S6 Heavy Bolters, etc.

==Thousand Sons Unit Tweaks==

Magnus: Magnus is boss, I'll grant that. The only thing I would change is a requirement that if you do take Magnus, he must be your Warlord, and he may only be fielded in a Thousand Sons detachment. I wrote a list with him, Typhus and Plague Zombies and that's just wrong.

Exalted Sorcerer: The Exalted Sorcerer may choose a Force Weapon of choice instead of just the Staff. Modify Lord of the Silver Tower as follows: Change the attack profile to: Range: Infinite, Strength 7, AP 2, Heavy 1, Blast, Barrage, Armorbane. The attack still requires Line of Sight as normal, and is no longer "Once Per Game"

Rubric Marines: The Aspiring Sorcerer gains an additional wound and an Inferno Boltgun to go alongside the Inferno Bolt Pistol. The Aspiring Sorcerer has a Force Weapon of choice. One Rubric Marine may take a Soulreaper Cannon; if the unit numbers 10 or more, a second Rubric Marine may take a Soulreaper Cannon. Warpflame Weapons are a "free swap".

Scarab Occult Terminators: The Sorcerer may chose a Force Weapon of Choice and may swap out the Inferno Combi-Bolter for a Power Weapon for 5 points. Scarab Occult Terminators replace their Power Sword for a Power Khopesh (S: User+1, AP 4, Rending). For every 5 models in this unit, up to 2 models may select a Heavy Warpflamer, Soulreaper Cannon, or Hellfyre Missile Rack. Optionally, allow them to be taken as the Terminator requirement for any Detachment requiring Terminators. Use them in a Terminator Annihilation Force or Black Legion Warband.

Tzaangors: Replace Relic Hunters with Bestial Fury: They gain +1 Strength and Initiative if they pass a Leadership check at the start of a Fight Sub-Phase. This replaces their "Bonus Strength/Initiative on Charge" bonus from their formation. Optionally, they could have Scout, to mimic "ambush" tactics of olde WHFB Beastmen.
-The Twistbray has 2 wounds base and Champion of Chaos, can take Melee Weapons from the Chaos Space Marines armory or a Gift of Mutation (no Meltabombs though), and may be upgraded to a ML 1 Psyker for +25 points.

==Thousand Sons Detachment==
=Requirements=
-Models that may take the Mark of Tzeentch must do so.
-Units with any Mark other than Tzeentch may not be taken.
-Daemon Princes must be Daemons of Tzeentch.
-Units that are Daemons of any other Chaos God may not be taken.
-Models with Daemonforge must be Daemons of Tzeentch at an extra +10 points per model.
-Models that may take Veterans of the Long War must do so at no additional cost.

=Benefits=
Legacy of the Rubric: All non-Character models with Veterans of the Long War gain Fearless. All non-character models with Veterans of the Long War that don't already have Relentless have Slow and Purposeful.

Blessing of Tzeentch: Psykers from a Thousand Sons detachment may alter the results of Perils by +-1. When rolling to determine which Psychic powers they know, they may adjust the result by +-1. Thousand Sons units my adjust the result by +-1 for any random charts encountered during movement, from Mysterious Objectives to Munitorium Armored Crates. Free Warp Charge for Blessings was a bit OTT/oddly specific for buffstars. Reducing random in Psyker powers gives them more consistency. The bonus for Crates/Mysterious Objectives shows how the Architect of Fate is more than just magic.

Loremasters of Tzeentch: Psykers in this detachment may generate up to all their powers from the Lore of Tzeentch; they must still generate at least one power from the Lore as normal.

==Grand Coven==
NOTE: Many of these formations will be modified to be a total of "9" units, one Independent Character + 8. This way it's "9" in total, especially since it's fairly possible to run certain characters "solo" in 40k, and it makes getting certain bonuses in 40k more attainable.

NOTE: Favored of Tzeentch is "when the maximum number of units in this formation is taken, models in the formation with the Mark of Tzeentch may re-roll 1s for Saves and models; Daemon of Tzeentch may re-roll all Invulnerable Saving throws in addition to the normal re-rolls of 1 granted from Daemon of Tzeentch"

=Restrictions=
-This is a Thousand Sons Detachment, and all units in this Detachment must adhere to the corresponding restrictions.
-Must take at least one Core and one Auxiliary. It may take up to 3 Command Choices.

=Benefits=
Lord of Fallen Prospero: Unchanged
Arcane Assault: When attempting to manifest a Witchfire or Malediction and you spend at least one Warp Charge point on it, you may elect to gain an additional Warp Charge Point for it for free. (Psychic powers don't scale as well with points, and 1k Sons are sacrificing "Guns" for this).

=Core Formations=
War Cabal: Ahriman/Sorcerer/Exalted Sorcerer, 1-3 units of Rubric Marines, 1-3 Maulerfiends/Forgefiends or units of Rubric Marines, 1-2 units of Rubric Marines or Scarab Occult Terminators, and 1 Sorcerer, Exalted Sorcerer, or units of Rubric Marines. Models in this detachment may not take Dedicated Transports, and you must take at least one unit of Rubric Marines for each Walker in this formation. The formation has Favored of Tzeentch and replaces Oracular Guidance with:
-Psychic Contagion: Whenever a friendly Thousand Sons Psyker manifests a blessing on a unit from this formation and it is not denied, you may immediately manifest that Blessing on an additional unit from this formation within 6" of the unit that received the initial blessing; this succeeds automatically/may not be denied.

Sekhmet Conclave: Magnus/Ahriman/Daemon Prince/Exalted Sorcerer, 1-3 units of Scarab Occult Terminators, 1-3 Helbrutes or units of Scarab Occult Terminators, and 1-3 Exalted Sorcerers or units of Scarab Occult Terminators. Units from this formation may not take Dedicated Transports. They keep Favored of Tzeentch, and Sorcerous Sigil-Wards is modified so that all 6s to wound/penetrate a unit within 6" of two other units from this formation are treated as 1s.

=Command Formations=
Lords of the Thousand Sons: Magnus, Ahriman, an Exalted Sorcerer, Sorcerer, or Lord.

Rehati War Sect: Magnus and 2-8 Daemon Princes/Exalted Sorcerers, that must be upgraded to ML 3. Units from this formation gain Favored of Tzeentch, Eternal Warrior, and ignore Line of Sight for powers while within 18" of Magnus. Removed the "Manifest on 3+ bonus for others" from the previous rules; this formation is more "fighty" than others.

Ahriman's Exiles: Ahriman and 2-8 Exalted Sorcerers. Same bonuses.

=Auxiliary Formations=
Replace Daemon Engines and the Helbrute entry from Legion Armory with the Heldrake Terror Pack and Helforged Warpack (Note: They do NOT get Favored of Tzeentch!). Add Rhinos to Legion Armory.

Add the Chaos Warband and the Terminator Annihilation Force as Auxiliary choices.

War Coven: 1-3 units of Chosen, 1-3 Exalted Sorcerers or units of Chosen, and 1-3 units of Chaos Terminators or units of Chosen. The Terminators must be at least 5 models strong, and may not be substituted for Scarab Occult Terminators. The formation gets Favored of Tzeentch, Relentless, the Chosen and Chaos Terminators get Brotherhood of Psykers, and the Formation gains the following benefit:
-Cult Affinity: At army creation, select a Cult for units from this formation to be a part of. A Cult has an associated Discipline, which members of that Cult must generate all of their powers from, overriding the need for models with the Mark of Tzeentch to generate all of their powers from one Discipline. Whenever a Psyker from this Formation that is composed of Thousand Sons from one or more detachments manifests a power from that Cult's discipline, all models in the Psyker's Unit gain a bonus that lasts until the start of the Thousand Son's next Psychic Phase. The Cults are: Corvidae (Divination; all models in the unit gain Precision Shots and Precision Strikes), Pyrae (Pyromancy; all Flamers in the unit gain -1 AP), Pavoni (Biomancy; all models in the unit Feel No Pain), Anathean (Telepathy; all models in the unit gain Interceptor), and Raptorae (Telekinesis; all models in the unit gain Hammer of Wrath, or an additional Hammer of Wrath attack if they already had it).

Metamorphic Mob: Replaces the Tzaangor Warherd. 1 Dark Apostle, 2-4 units of Tzaangors, 1-2 units of Tzaangors or Spawn, and 1-2 units of Tzaangors or Possessed. In exchange, they have the following abilities: Favored of Tzeentch, "Run and Charge", and the following rule:
-Nexus of Change: Every unit in this formation has a Special Ability that extends to all units from this formation within 9" of it. The Dark Apostle grants Zealot to all units from this formation within 9", the Spawn have Hit & Run and grant it to all units from this formation within 9" the Tzaangors gain their Bestial Fury all units from this formation within 9", and the Possessed grant their Vessels of Chaos ability to all units from this formation within 9".

Spireguard Besiegers: 2 units of Chaos Cultists, 1-4 Obliterators/Mutilators/units of Chaos Cultists (note: This means you can only take "solo" Obliterators/Mutilators), and 1-3 Defilers/units of Chaos Cultists. The Formation gains Favored of Tzeentch, and each Mutilator/Obliterator you take must be attached to a Chaos Cultist unit from that formation, replacing the unit's Cultist Champion, and no more than one Obliterator/Mutilator can be attached to each Cultist unit; in exchange, they gain the (Character) subtype and Champion of Chaos special rules. Cultists get free Wargear. Defilers within 6" of one or more Chaos Cultists from this formation may direct attacks onto that Cultist/unit as though it had Look Out, Sir!

One thing I wanted to do is a formation for the Hidden Ones but I am unsure how to go about implementing it.

BONUS: Nerfing Heralds Anarchic: Each Herald from Heralds Anarchic generates an additional Warp Charge Point; each additional Warp Charge generated from this formation may only be used by the Herald in question. No using "Heralds+Blue Horrors" as "4 Warp Charge for 100 points" as a battery for Magnus!

Tzeentch's Firestorm-Seems okay. Might be a tad strong for WC 1, but you are of the GOD OF MAGIC, so...

Boon Of Mutation-Yeah, seems fine.

Siphon Magic-Eergh... I'm not sure I like the change. Especially since, with a Spell Familiar, you can get it off reasonably reliably with 3 Warp Charges, meaning it's essentially free.

Forbidden Lore is fine.

Not sure I like the Warpflamer change. I think the reduced AP is better than increased strength.

Icon Of Flame seems okay. Bolt weapons still aren't that scary, and Warpflame is not good, so... I guess it's good?

Magnus is fine.

Exalted Sorcerer changes are fine (for the Force Weapon change) and too much, for the S7 AP2 Armourbane at-will attack. Barrage means it actually DOESN'T need Line of Sight, and even if it does, it's still crazy good at sniping out characters or special weapons. Although I notice it's not Blast or anything-is that a mistake?

Rubric Marine changes seem fine.

SOT changes seem fine.

I'm not sure about giving the Twistbray a Mastery Level. That seems a little excessive.

Blessing of Tzeentch is way too much. This virtually guarantees them the powers they want, and makes Perils much less threatening. (ML 3 has a 75% chance of getting Invisibility, and Ahriman has just under 90%.)

Arcane Assault... I don't like it. It's basically guaranteed going off of any WC 1 witchfire with a spell familiar (and damn good chances even without).

Psychic Contagion is ridiculous, as written. You can now grant Iron Arm to an entire unit!

Sorcerous Sigil-Wards is too much, since it makes Rending literally useless, and this formation includes terminators. Plus it makes them totally immune to low-strength weaponry, since they need 6s to wound, which are treated as 1s.

Overall, I think these changes push TSons too far into godly.

 JNAProductions wrote:
Siphon Magic-Eergh... I'm not sure I like the change. Especially since, with a Spell Familiar, you can get it off reasonably reliably with 3 Warp Charges, meaning it's essentially free.

The change is mostly to nerf the "Magnus and Batteries" build. I wrote a list that was: Typhus & Zombies, Magnus, and a ton of Heralds Anarchic/Blue Horrors. Magnus cast Siphon first, everything else cast stuff, then Magnus used the free Warp Charge (which stacked up FAST) to blast things.

 JNAProductions wrote:
Not sure I like the Warpflamer change. I think the reduced AP is better than increased strength.

4+ saves are the exception rather than the norm. You're also making it a "free swap". 7 points to replace an AP 3 Bolter with an AP 4 Flamer, in an edition where you can only remove models in range of the flamer, the model with said Flamer is Slow and Purposeful, AND the Flamer has Warpflame, makes me honestly wonder what drugs Simon Grant took when writing Wrath of Magnus!

 JNAProductions wrote:
Icon Of Flame seems okay. Bolt weapons still aren't that scary, and Warpflame is not good, so... I guess it's good?

The big winner would be Heavy Bolter Havocs. They'd basically be move-and-fire at S6. Vanilla 1k Sons can also benefit, as they fit the "Dark Reaper" niche a little better.

 JNAProductions wrote:
Exalted Sorcerer changes are fine (for the Force Weapon change) and too much, for the S7 AP2 Armourbane at-will attack. Barrage means it actually DOESN'T need Line of Sight, and even if it does, it's still crazy good at sniping out characters or special weapons. Although I notice it's not Blast or anything-is that a mistake?

Added small blast. Characters can still LOS. I added a "Requires Line of Sight." The fluff for the ability mentions it being a beam of energy striking from orbit...but in-game, it's basically a direct-fire plasma cannon. S7 instead of 9 to prevent Instant-Deathing stuff of note.

 JNAProductions wrote:
I'm not sure about giving the Twistbray a Mastery Level. That seems a little excessive.

The option is there to purchase it for +25 points. Note, no Force Weapons are being added alongside.

 JNAProductions wrote:
Blessing of Tzeentch is way too much. This virtually guarantees them the powers they want, and makes Perils much less threatening. (ML 3 has a 75% chance of getting Invisibility, and Ahriman has just under 90%.)

Invisibility is a trouble spell. I do prefer nerfing it (especially ITC Invis) but it's still a thought.

 JNAProductions wrote:
Arcane Assault... I don't like it. It's basically guaranteed going off of any WC 1 witchfire with a spell familiar (and damn good chances even without).

Honestly, I'd rather they witchfire than attempt for psychic deathstars.

 JNAProductions wrote:
Psychic Contagion is ridiculous, as written. You can now grant Iron Arm to an entire unit!

The RAW is strictly for Psychic Powers which target an entire unit (so stuff like Force, Prescience, Invisibility, etc). Stuff like Iron Arm, no. I can edit Siphon Magic to target "The Psyker" as well, to prevent "double Warp Charge" bonuses too.

 JNAProductions wrote:
Sorcerous Sigil-Wards is too much, since it makes Rending literally useless, and this formation includes terminators. Plus it makes them totally immune to low-strength weaponry, since they need 6s to wound, which are treated as 1s.

How many S2 weapons are there in 40k? For S3 and S4 versus T4, "Dropping 6s" has the same mathhammer as just adding +1 toughness. The rending immunity is intentional but it also gives resilience versus Grav and Poison. S8 inflicts ID though (so FNP buffs are a no-go. Iontides will be better-off as a result). Also, consider that Blessing of Tzeentch is no longer a 3++. To take full advantage of the formation requires being in super-tight unit cohesion of course, risking Objective games of course, and that can normally be negated through shenanigans (move powers, tank shock, assault/forcing pile-ins, etc). Definitely bears testing though. The other side-effect is making Helbrutes immune to Grav, which they honestly could use IMO.

Flechette Blasters. And... Um... Ratlings in CC.

The bigger issue is the tougher stuff-like Magnus. He's now immune to anything less than S6.

 JNAProductions wrote:
Flechette Blasters. And... Um... Ratlings in CC.

The bigger issue is the tougher stuff-like Magnus. He's now immune to anything less than S6.

One thing I'm contemplating is modifying the rule to require being within 6" of at least two units of SOT from the formation, Magnus would be tricky of course, but he'd be on a tighter leash of course (and chances are you want to kill the Terminators first anyway, as they're a WC battery as much as anything else).

Another issue with it, is that it affects things like Poison, that usually don't care about toughness.

Edit: Which isn't INHERENTLY bad, but it seems too powerful to me.

 JNAProductions wrote:
Another issue with it, is that it affects things like Poison, that usually don't care about toughness.

Edit: Which isn't INHERENTLY bad, but it seems too powerful to me.

It also does mean stuff like Helbrutes with de-facto immunity to Grav or Scatter Lasers...which honestly they could use.

Either way, it's definitely something for playtesting against.

Thoughts on the Auxiliaries btw? Spireguard Besiegers is a very kludge formation with a lot of weird interactions in it, while Metamorphic Mob is very comedic in its implications.

I'm with the above in that the +/-1 choices are broken, 'No rolls of 6' is broken, and your understanding of the rules and the way that you wrote Psychic Contagion means that it is still, in fact, broken - Units can be a single model. If a Psyker casts a power on himself, he's still casting that power on 'A unit'.

To make my point with the +/-1, consider this:
It makes it impossible to get the worst result on Perils, and means that, a full 50% of the time, you won't even take a wound! A whopping 1/3rd of the time, you'll actually benefit from getting Perils of the Warp, which is simply a massive step upward. That's just too good of a benefit, especially if you're spamming Summoning powers, one of the only weaknesses of which is that you take a lot of wounds from Perilsing.

Meanwhile, it makes Cheesestars a lot more viable and powerful. If you want a power that's either a 1 or a 6 on the chart, you have a 2/3rds chance of getting it. But if your power is a 2-5? You have a 50/50 chance of getting that power on any given roll. If you're rolling on a chart and want one of two different powers from it, (Say, rolling on Biomancy to get Enfeeble or Endurance,) you literally cannot fail.
To make a small digression here, the biggest complaint about the Psychic Phase is that the powers are too variable in power level. Certain abilities are always going to be extremely useful, but others are going to be situational or just useless in any context. Scriers Gaze is just never going to compare to Prescience, and neither of those are going to compare to Invisibility. There's a reason nobody rolls on Pyromancy - The best powers are average, and many of them are weak.

The only upside to this imbalance is that it creates certain kinds of 'Interesting' play, and prevents Psykers from *completely dominating the game. Because you can't be 100% certain that you'll get the exact power that you want (unless it's your Primaris,) you also can't rely entirely on that Psyker to do what you need him to, and may need to adapt or have several potential roles available for him to fill based off of what you want to do. In the most extreme cases, players bring several Psykers at a time, using most of them as batteries in the hope that just one will roll the power that they need. This is an inherent amount of balance in the way the system works.

The IDEAL here of course would be that all powers were equally useful, depending on context, and that Psykers could select them from the getgo or randomize - Either way, they would have the same amount of potential. This would change them from 'Deathstar ingredient' to 'Swiss-army knife' that lets players fill holes at the beginning of games as needed. But, that's not the game we have.


With that digression out of the way... You do see the problem, right? You're effectively giving out the ideal powers for free, to an army that already has overwhelming psychic strength. Your overpowered version of Siphon Magic will be cast on almost every unit, since half the psykers in the game are going to take it. Invisibility will become an army-wide buff, since the player is going to have their number of warp charges increased by about 30%, and every psyker in their army is going to have Invisibility on hand to go with it.


As for making 6s into 1s, that's just a bad way of balancing things. Most weapons that have some kind of special damage effect only get that effect on a roll of '6'. Rending weapons become useless, along with any other weapon that becomes AP2 or causes damage on a 6 - Since some players rely on those weapons to be viable at all, that's a huge crippler.
It makes you effectively immune to D weapons, which absolutely should not be the case.
It makes your Magnus and/or Daemon Prince literally unkillable by most conventional means, and effectively unkillable by all others. Even your other units can be brought up to insane overpoweredness by just casting Fleshmetal hide.


In short: The things that were broken before are still broken. The things that are new are also broken. Your new version of Siphon Magic is slightly better than your old version, but still pretty OP by comparison.

The heralds thing could probably even be fixed by having to pay a little extra for it. It's 25pt per level in the daemon book, as they just get an additional power but not mastery level, perhaps 15pts extra per herald works too? I actually like how AoS makes you pay for formations in general and think it'd be a nice change if 8th brought it in.

I can go back and edit Psychic Contagion to clarify that it only works for blessings that "target a unit", rather than those that target "the Psyker's Unit", "the Psyker", or any other variant thereof. It would be ultimately an upgrade to Oracular Guidance, which was effectively Limited Prescience that triggered on casting any power (of course, a good deal of that power could be replicated with an Armored Crate, so...)

Other thoughts:

I'm not seeing rhe "no 6s" effect being broken for what it requires. The only army I can see over relying on Rending is...Genestealer Cults? That said, if it proves too generous, make it being within 3" of two units of SoT, rather than 6. This does make them very durable against a lot of stuff, but actually taking advantage of this requires a massive sacrifice to your board presence. Plus it's not like you can't negate it via Tank Shock, assault from the right vectors (Pile in is a 3" move after all), etc.

Since Invisibility and other Deathstar powers are a thing, limit the "powers known" +-1 modifier to powers from the Lore of Change. Alternately, restrict the +-1 modifier to only being used to obtain a Witchfire.

The modifier to Perils actually slightly lowers the chances of not taking a wound. A 5+ rerollable is slightly better than a 4+ after all. It does up the chance of becoming Ultraman for a turn...but honestly I'm mostly cool with that. Bears testing of course.

The original version of Siphon Magic is basically awesome for Magnus, and useless for ML 1 Psykers. This version removes the "may cast an additional power" option from the original version, so it does become a tradeoff between casting it or a relevant power. I could alternately just be fine with reverting it to its base implementation, especially if the +-1 modifier to Tzeentch for getting Witchfires is a thing; modify the basic version of Siphon Magic so that you only get additional dice from *other* friendly casters within 9" from the same detachment, so you don't get free dice for casting Siphon Magic, or from Daemons casting, and maybe add a clause where if one or more casters are eligible to gain a die from Siphon Magic, only one model gets that die. Make "shuffling tokens" work a little more like Focus for Convergence of Cyriss; you "could" maintain a powerful assault if you keep your units in formation, do your powers in precise order, account for Mastery Levels limiting how many casters can cast, etc.

Overall though, I'm more interested in whatever can he done to buff basic Rubrics (the floor) instead of the Ceiling.

Automatically Appended Next Post:

 n0t_u wrote:
The heralds thing could probably even be fixed by having to pay a little extra for it. It's 25pt per level in the daemon book, as they just get an additional power but not mastery level, perhaps 15pts extra per herald works too? I actually like how AoS makes you pay for formations in general and think it'd be a nice change if 8th brought it in.

Personally I'm against point costs for formations, since they either don't scale well to point games, or then involve percentages and that gets awkward. I do prefer more restrictions, drawbacks in exchange for bonuses (think: Rites of War, or the Corsair Raiding Detachment), or other oddities.

For example: another restriction with Heralds could be that each Herald must cost at least 100 points, and they may not take identical combinations of upgrades. Something like that, similar to the 3e Andy Chambers Ork Codex where the Big Mek could take a squad of Mekboyz, but they could not take the same combinations of wargear (as no self-respecting Mek would copy their competitor...ahem).

That, or they're only allowed to roll on the Discipline of Change. Losing access to Divination and Malefic Daemonology is arguably worse than getting a free Warp Charge to use for casting Flickerfires.

 MagicJuggler wrote:
I can go back and edit Psychic Contagion to clarify that it only works for blessings that "target a unit", rather than those that target "the Psyker's Unit", "the Psyker", or any other variant thereof. It would be ultimately an upgrade to Oracular Guidance, which was effectively Limited Prescience that triggered on casting any power (of course, a good deal of that power could be replicated with an Armored Crate, so...)

Okay, sure. I'm still not sure you want units to be able to chain together Invisibility, but that's another can of worms.

Other thoughts:

I'm not seeing rhe "no 6s" effect being broken for what it requires. The only army I can see over relying on Rending is...Genestealer Cults? That said, if it proves too generous, make it being within 3" of two units of SoT, rather than 6. This does make them very durable against a lot of stuff, but actually taking advantage of this requires a massive sacrifice to your board presence. Plus it's not like you can't negate it via Tank Shock, assault from the right vectors (Pile in is a 3" move after all), etc.

You can make the radius as small as you like, it's still going to have the same problem: Too much durability. Your psykers have access to a power that grants unit-wide +1 Toughness, after all. Even against baseline Terminators, I'm now wounding on just 5s if I am using anyone at S3. Say, y'know, the armywide strength of most models that isn't Space Marines?
In fact, I'm inclined to say that auto-failing rolls of 6 is more potent than forcing a re-roll of all wounds. It's less good against high strength fire, sure, but in exchange you're getting nigh-invulnerability to all low-strength mass firepower, invulnerability to all rending weapons, (And on top of that, Bladestorm and several other 'AP2 on to-wounds of 6' rules that I'm forgetting,) and anything else.

And sure, if you make the radius tiny enough, it's not going to matter, but that just makes the formation useless. It's a balance problem: If you make the radius large enough to be viable, then it's overpowered. If it's too small to be used in any context, then it's useless.

Since Invisibility and other Deathstar powers are a thing, limit the "powers known" +-1 modifier to powers from the Lore of Change. Alternately, restrict the +-1 modifier to only being used to obtain a Witchfire.

Why not just allow re-rolls on powers? It's not as obscenely powerful, but still allows players more choice on what abilities they get.

The original version of Siphon Magic is basically awesome for Magnus, and useless for ML 1 Psykers. This version removes the "may cast an additional power" option from the original version, so it does become a tradeoff between casting it or a relevant power. I could alternately just be fine with reverting it to its base implementation, especially if the +-1 modifier to Tzeentch for getting Witchfires is a thing; modify the basic version of Siphon Magic so that you only get additional dice from *other* friendly casters within 9" from the same detachment, so you don't get free dice for casting Siphon Magic, or from Daemons casting, and maybe add a clause where if one or more casters are eligible to gain a die from Siphon Magic, only one model gets that die. Make "shuffling tokens" work a little more like Focus for Convergence of Cyriss; you "could" maintain a powerful assault if you keep your units in formation, do your powers in precise order, account for Mastery Levels limiting how many casters can cast, etc.

See, I don't see having one sometimes-useless power as being much of a problem. Most charts have one power that's either effectively or literally useless some of the time. Precognition isn't going to help on an Astropath. Scrier's Gaze won't help in a normal game with no reserves. All the powers that give Haywire are useless against armies without vehicles. Telekine Dome is useless in an all-Terminator army. Mental Fortitude doesn't help Space Marines. Banishment is no good if you're not facing Daemons. Pyromancy is no good unless your opponent is playing with a handicap.
So having a power that is very useful for your Sorcerers, but mediocre or useless on weaker psykers? Not a problem. That's what the Primaris power is for

Waaaghpower wrote:
Okay, sure. I'm still not sure you want units to be able to chain together Invisibility, but that's another can of worms.

It is a can of worms, agreed. Personally, I feel ITC Invisibility does a lot to fix it, but it's still definitely a point of contention.

Waaaghpower wrote:
You can make the radius as small as you like, it's still going to have the same problem: Too much durability. Your psykers have access to a power that grants unit-wide +1 Toughness, after all. Even against baseline Terminators, I'm now wounding on just 5s if I am using anyone at S3. Say, y'know, the armywide strength of most models that isn't Space Marines?

The *melee* strength of most models, to be more clear. I've also almost never seen an Eldar army with Bladestorm nowadays (other than the Farseer/Autarch that is), which is kind of crazy tbh.

Waaaghpower wrote:
Why not just allow re-rolls on powers? It's not as obscenely powerful, but still allows players more choice on what abilities they get.

I'd be ok with it, especially if Tzeentch's Firestorm is modified to basically be "Warpfire Smite". Worst comes to worst, your Psyker can at least do *something*. Everything else (Perils Results, Mysterious Objectives/Terrain, Armored Crates, etc) would be a reroll instead of a +-1 modifier then. In fact, that does seem more fluff-appropriate that while Tzeentch might adjust fate in your favor, you don't get to know what he's doing in advance!

Waaaghpower wrote:
See, I don't see having one sometimes-useless power as being much of a problem. Most charts have one power that's either effectively or literally useless some of the time. Precognition isn't going to help on an Astropath. Scrier's Gaze won't help in a normal game with no reserves. All the powers that give Haywire are useless against armies without vehicles. Telekine Dome is useless in an all-Terminator army. Mental Fortitude doesn't help Space Marines. Banishment is no good if you're not facing Daemons. Pyromancy is no good unless your opponent is playing with a handicap. So having a power that is very useful for your Sorcerers, but mediocre or useless on weaker psykers? Not a problem. That's what the Primaris power is for

This is a different discussion altogether, but IMO half the problem is that some disciplines are just worse than others! The problem with Telekinesis/Pyromancy, versus Divination/Telepathy/Malefic, is that you have some powers with bad Primaris Powers and ok-to-decent powers you can roll for, versus some disciplines with potentially incredible powers with good primaris powers to fall back on. Aka "I can roll for Invisibility, and if I get a power that's useless, I still fall back on Psychic Shriek." "I can roll for Sacrifice and if I get Dark Gaze, I can fall back on Summoning." "I can roll for Precognition/Perfect Timing/Misfortune and if I get a power I don't like, I can fall back on Prescience." Versus "I can roll for...Psychic Maelstrom I guess? Eh, I guess Assail isn't the worst..." Or "I can roll for Doombolt or Treason of Tzeentch...Siphon Magic? But I'm ML 1, this power literally does nothing for me. Guess I'll fall back on Tzeentch's Firestorm (arguably the worst Witchfire in the game)"

The real issue is I can build a list like: http://www.dakkadakka.com/dakkaforum/posts/list/711315.page or some other variant where you're aiming for a "Minimum Tax for Magnus" and cramming as many additional Warp Charge in as you can. Magnus casts Siphon Magic on 2 dice. Each time another unit casts (it's easy to remain within 18" of a good deal of your army), he gains a die. 7 dice apiece is enough for several summons, or 3 dice apiece for each Sacrifice you throw down. Based on RAW, Magnus might even benefit himself each time he casts Siphon Magic. So I'd rather a Siphon Magic that is at least "usable" for ML 1 (rather than being literally useless, 100% of the time). That, or make a super-limited version of it a bonus for Thousand Sons detachments, and replace the power with something else:

The alternate idea would be to add the following as a bonus for Thousand Sons detachments:

Psychic Ritual: Whenever a Thousand Sons Psyker successfully manifests a power which is not denied but before resolving the effects of the power, place a token on another friendly 1k Sons Psyker within 9" of that Psyker. Whenever that Psyker attempts to manifest a power, spending at least one Warp Charge point from the pool as normal, the Psyker may spend any number of tokens on him as additional Warp Charge Points. Discard any unused tokens at the end of the Psychic Phase.

Alternately, make Psychic Ritual the bonus for the War Cabal, rather than the "Free Dice" for Witchfires, and make the "Free Dice for Witchfires" the War Cabal bonus instead of the "Double-Blessings".

And then replace Siphon Magic as a power altogether with:
Webwarp: Webwarp is a WC 1 Blessing that targets a friendly unit within 18". Immediately remove that unit from the table; it arrives as per Deep Strike but does not Scatter, place the first model entirely within 6" of the Psyker that cast Webwarp.

Something in favor of the current Siphon Magic, though:
Siphon Magic will never, ever increase the amount of Warp Charges that a single Psyker has access to. If you have several psykers cast Siphon Magic, you can end up with more Warp Charges than you started with armywide, but never for any individual Psyker. (I suppose you might be able to start a recursive loop if you have four or five psykers all casting Siphon Magic in a circle, then casting 1-WC powers all around while singing kum-ba-yah, but if you do that then you're going to run out of possible manifests before you accomplish much.)

So while you can drop Magnus in the middle of your army and have him siphon away, you're not going to get more Warp Charges than you started with. Say you've got an army with 25+d6 Warp Charges (Not the most possible, but still fairly high,) you need 2 to cast Siphon Magic, 3 if you really don't want it getting denied. Then, everyone else is going to take 5 Warp Charges per summon, since they all have Spell Familiars. You're getting five Warp Charges back before you're out of Warp Charges.
If they cast lower-cost spells, say, ML1, then it pays off better. You might get ten Warp Charges back. Ten Warp Charges is nothing to sneeze at, but it's as part of an army with an average of 28 to begin with - About a 35% boost.

I've been getting feedback from some other sources, and one other idea I've received is...just drop Ahriman's Exiles and the War Sect altogether. I would personally be ok with this tbh.

One of the big reasons 1k Sons are such a mess-up is that of the new formations, 3 of them are just "Take a lot of Psyker characters", one is "Take a lot of Sorcerers"...There's a startling lack of creativity on the part of GW in that regard.

Updated after thinking about things even further.

==Psychic Powers==

Tzeentch's Firestorm:Tzeentch's Firestorm is a ML 1 Witchfire with the following profile: Range 18, Strength 5, AP 3, Assault 1, Blast, Warpflame, Inferno: Inferno: A model that the hole of the blast is centered over takes a single S9 AP 2 hits instead of a single S5 AP 3 hit. This is basically the Librarius/Primaris, with the option to get a Lascannon Hit on the "Center" target in exchange for risking granting Warpflame. Fluffwise, the power is written up as "a storm of pink and blue fire" and this made sense also.

Boon of Mutation: Remove the Strength 4 hit from the ability. When you roll for a Chaos Boon, you may re-roll one die or the other.

Webwarp: Webwarp replaces Siphon Magic, and is a ML 1 Blessing that targets a friendly unit within 18" of the Psyker. Immediately remove that unit from the board (even if engaged in close combat) and place it on the board as though arriving from Deep Strike. The first model must he placed within 6" of the Psyker, and the unit does not scatter.

-Add restrictions to Treason of Tzeentch or other mind-control powers to prevent them from hitting the same unit multiple times in the same Psychic Phase. No stacking with Shroud of Deceit!

=Warlord Traits=

Forbidden Lore: Append the following: If your Warlord was not a Psyker, your Warlord is now treated as a Mastery Level 1 Psyker that must generate a power from the Lore of Tzeentch.

==Wargear==

Mark of Tzeentch: The Mark of Tzeentch adds +1 to Invulnerable Saves, or a 5+ Invulnerable should the model not previously have access to it. Characters without the Psyker USR may be upgraded to a Psyker with Mastery Level 1 for +25 points.

Warpflamer Weapons: Are equivalent to weapons of their normal type, but with +1 Strength, and Warpflame. This means a Warpflamer is S5 AP 5, a Heavy Warpflamer is S6, AP 4, etc.

Icon of Flame: The simple tweak would be to replace "Soul Blaze" with "+1 Strength & Warpflame", for S5 Inferno Boltguns, S6 Heavy Bolters, etc.

==Thousand Sons Unit Tweaks==

Magnus: Magnus is boss, I'll grant that. The only thing I would change is a requirement that if you do take Magnus, he must be your Warlord, and he may only be fielded in a Thousand Sons detachment. I wrote a list with him, Typhus and Plague Zombies and that's just wrong.

Exalted Sorcerer: Any previous detachment that allows a Sorcerer may take a Sorcerer instead, provided all other detachment requirements are met. For example, a Black Legion Warband could take an Exalted Sorcerer, but a Terminator Annihilation Force would not be able to. The Exalted Sorcerer may choose a Force Weapon of choice instead of just the Staff. Modify Lord of the Silver Tower as follows: Change the attack profile to: Range: Infinite, Strength 7, AP 2, Heavy 1, Blast, Barrage, Armorbane. The attack still requires Line of Sight as normal, and is no longer "Once Per Game"

Rubric Marines: The Aspiring Sorcerer gains an additional wound and an Inferno Boltgun to go alongside the Inferno Bolt Pistol. The Aspiring Sorcerer has a Force Weapon of choice. One Rubric Marine may take a Soulreaper Cannon; if the unit numbers 10 or more, a second Rubric Marine may take a Soulreaper Cannon. Warpflame Weapons are a "free swap".

Scarab Occult Terminators: The Sorcerer may chose a Force Weapon of Choice and may swap out the Inferno Combi-Bolter for a Power Weapon for 5 points. Scarab Occult Terminators replace their Power Sword for a Power Khopesh (S: User+1, AP 4, Rending). For every 5 models in this unit, up to 2 models may select a Heavy Warpflamer, Soulreaper Cannon, or Hellfyre Missile Rack. Optionally, allow them to be taken as the Terminator requirement for any non-new Detachment requiring Terminators. Use them in a Terminator Annihilation Force or Black Legion Warband.

Tzaangors: Tzaangors have Leadership 6, and the Twistbray has Leadership 7. Gain Scout and Bestial Fury: They gain +1 Strength and Initiative if they pass a Leadership check at the start of a Fight Sub-Phase. This replaces their "Bonus Strength/Initiative on Charge" bonus from their formation.
-Rework Relic Hunters so that any time they come across terrain with a mysterious effect (Mysterious Objectives, Munitorium Armored Crates, etc), they may choose to modify the roll by +-1.
-The Twistbray has 2 wounds base and Champion of Chaos, can take Melee Weapons from the Chaos Space Marines armory or a Gift of Mutation (no Meltabombs though).

==Thousand Sons Detachment==
=Requirements=
-Models that may take the Mark of Tzeentch must do so.
-Units with any Mark other than Tzeentch may not be taken.
-Daemon Princes must be Daemons of Tzeentch.
-Units that are Daemons of any other Chaos God may not be taken.
-Models with Daemonforge must be Daemons of Tzeentch at an extra +10 points per model.
-Models that may take Veterans of the Long War must do so at no additional cost.

=Benefits=
Legacy of the Rubric: All non-Character models with Veterans of the Long War gain Fearless. All non-character models with Veterans of the Long War that don't already have Relentless have Slow and Purposeful.

Blessing of Tzeentch: Psykers from a Thousand Sons detachment may adjust the result by +-1 when rolling to generate Powers from the Lore of Tzeentch. Thousand Sons Psykers may reroll the result of Perils of the Warp.

Loremasters of Tzeentch: Psykers in this detachment may generate up to all their powers from the Lore of Tzeentch; they must still generate at least one power from the Lore as normal.

==Grand Coven==

NOTE: Most these formations have a unit that limits how many other units the formation may take. Basically, this means at least half the units chosen for that formation must be that unit. For example, the War Cabal has a restriction that you must have at least one Rubric Marine unit for each non-Rubric Marine unit you take. This restriction takes the mandatory "HQ" character into account. This means the War Cabal will require at least three units of Rubric Marines; 2 Exalted Sorcerers, one Rubric Marine unit, one Scarab Occult Terminator unit and one Forge fiend would violate that main restriction.

NOTE: Favored of Tzeentch is "when the maximum number of units in this formation is taken, models in the formation with the Mark of Tzeentch may re-roll 1s for Saves and models; Daemon of Tzeentch may re-roll all Invulnerable Saving throws in addition to the normal re-rolls of 1 granted from Daemon of Tzeentch"

=Restrictions=
-This is a Thousand Sons Detachment, and all units in this Detachment must adhere to the corresponding restrictions.
-Must take at least one Core and one Auxiliary. It may take up to 3 Command Choices.

=Benefits=
Lord of Fallen Prospero: Unchanged
Psychic Ritual: When a Psyker from this detachment successfully manifests a power and it is not denied, immediately before resolving the power, select another Psyker from this detachment that is within 9" of the first Psyker, and place a token on that Psyker. These tokens may be spent as "additional Warp Charge" points, provided the Psyker in question spends at least one Warp Charge as normal. Remove any such unused tokens at the end of the Psychic Phase.

=Core Formations=
War Cabal: Ahriman/Sorcerer/Exalted Sorcerer, 1-3 units of Rubric Marines, 1-3 Maulerfiends/Forgefiends or units of Rubric Marines, 1-2 units of Rubric Marines or Scarab Occult Terminators, and 1 Sorcerer, Exalted Sorcerer or unit of Rubric Marines. This formation requires at least one unit of Rubric Marines in this formation for each non-Rubric Marine unit in the same formation (excluding Dedicated Transports). The formation has Favored of Tzeentch, Split Fire, and replaces Oracular Guidance with:
-Arcane Assault: Forgefiends/Maulerfiends in this formation have Psychic Pilot with Mastery Level 1. Whenever a Psyker from this formation attempts to manifest a Witchfire and spends at least one Warp Charge as normal, that Psyker may immediately add an additional die to the manifestation attempt for free.

Sekhmet Conclave: Magnus/Ahriman/Daemon Prince/Exalted Sorcerer, 1-3 units of Scarab Occult Terminators, 1-3 Helbrutes or units of Scarab Occult Terminators, and 1-3 Exalted Sorcerers or units of Scarab Occult Terminators. Units from this formation may not take Dedicated Transports, and this formation requires at least one unit of Scarab Occult Terminators for each non-Scarab Occult Terminator unit from the same formation. They keep Favored of Tzeentch, and Sorcerous Sigil-Wards is modified so that all 6s to wound/penetrate a unit within 6" of two other units of Scarab Occult Terminators from this formation are treated as 1s.

=Command Formations=
Lords of the Thousand Sons: Magnus, Ahriman, an Exalted Sorcerer, Sorcerer, or Lord.

Drop the Rehati War Sect and Ahriman's Exiles.

=Auxiliary Formations=
Replace Daemon Engines and the Helbrute entry from Legion Armory with the Heldrake Terror Pack and Helforged Warpack (Note: They do NOT get Favored of Tzeentch!). Add Rhinos to Legion Armory.

Add the Chaos Warband and the Terminator Annihilation Force as Auxiliary choices.

War Coven: 1 Exalted Sorcerer, 1-3 units of Chosen, 1-3 Sorcerers or units of Chosen, and 1-3 units of Chaos Terminators or units of Chosen. You must take at least one unit of Chosen for each non-Chosen unit in this formation, the Terminators must be at least 5 models strong, and Champions in this formation may not purchase additional Mastery Levels. The formation gets Favored of Tzeentch, Relentless, the Chosen and Chaos Terminators get Brotherhood of Psykers, and the Formation gains the following benefit:
-Cult Affinity: At army creation, select a Cult for units from this formation to be a part of. A Cult has an associated Discipline, which members of that Cult must generate all of their powers from, overriding the need for models with the Mark of Tzeentch to generate all of their powers from one Discipline. Whenever a Psyker from this Formation that is composed of Thousand Sons from one or more detachments manifests a power from that Cult's discipline, all models in the Psyker's Unit gain a bonus that lasts until the start of the Thousand Son's next Psychic Phase. The Cults are: Corvidae (Divination; all models in the unit gain Precision Shots and Precision Strikes), Pyrae (Pyromancy; all Flamers in the unit gain -2 AP), Pavoni (Biomancy; all models in the unit Feel No Pain), Anathean (Telepathy; all models in the unit gain Interceptor), and Raptorae (Telekinesis; all models in the unit gain Hammer of Wrath, or an additional Hammer of Wrath attack if they already had it).

Metamorphic Mob: Replaces the Tzaangor Warherd. 1 Dark Apostle, 1-3 units of Tzaangors, 1-3 units of Tzaangors or Possessed, and 1-3 units of Tzaangors or Spawn. You must have at least one unit of Tzaangors for each non-Tzaangor option in this formation, and each Spawn must take at least three models. The formation has Favored of Tzeentch, "Run and Charge", and Bestial Fury (Tzaangors may roll a 3rd die and drop the highest for the Leadership test to activate it).

Spireguard Besiegers: 1 Warpsmith, 2 units of Chaos Cultists, 1-4 Obliterators/Mutilators/units of Chaos Cultists (note: This means you can only take "solo" Obliterators/Mutilators), and 1-3 Defilers/units of Chaos Cultists. This formation must include at least one unit of Chaos Cultists for each non-unit of Chaos Cultists. The Formation gains Favored of Tzeentch, and each Mutilator/Obliterator you take must be attached to a Chaos Cultist unit from that formation, replacing the unit's Cultist Champion, and no more than one Obliterator/Mutilator can be attached to each Cultist unit; in exchange, they gain the (Character) subtype and Champion of Chaos special rules. Models in this formation get free Wargear (they must pay for Marks/Daemon of Tzeentch as normal, and Characters must pay for Mastery Levels as normal). Defilers within 6" of one or more Chaos Cultists from this formation may direct attacks onto that Cultist/unit on a 4+ as though it had Look Out, Sir! On a successful roll, remove the Cultist model outright.

One thing I wanted to do is a formation for the Hidden Ones but I am unsure how to go about implementing it.

BONUS: Nerfing Heralds Anarchic: Each Herald from Heralds Anarchic generates an additional Warp Charge Point; each additional Warp Charge generated from this formation may only be used by the Herald in question. Models from this formation may only generate powers from the Lore of Change. No using "Heralds+Blue Horrors" as "4 Warp Charge for 100 points" as a battery for Magnus!

 MagicJuggler wrote:
Drop the Rehati War Sect and Ahriman's Exiles

Um... why, exactly?

Yoyoyo wrote:

 MagicJuggler wrote:
Drop the Rehati War Sect and Ahriman's Exiles

Um... why, exactly?

The game has enough Cabalstar and Flying Circus variants as is
I would honestly prefer that either character be taken as part of a full Thousand Sons army, rather than being taken with "minimum tax" for what is functionally a Daemon army.

Ahriman's Exiles "might" be OK to keep in, as they could easily be fluffed as Psykers-for-hire. *shrug*

Yeah, but now there are no command formations at all. Oops? There's also no pure psyker formations, given that you turned War Coven into Chosen spam. Finally... you replaced the Sorcerer in the Warherd with an Apostle. I see a pattern in your changes, I just don't see the logic behind it.

GW clearly designed TS as 1) Sorcerers, 2) bodyguards, and 3) minor vehicle support.

What is the problem with that thematic vision?

Yoyoyo wrote:
Yeah, but now there are no command formations at all. Oops? There's also no pure psyker formations, given that you turned War Coven into Chosen spam. Finally... you replaced the Sorcerer in the Warherd with an Apostle. I see a pattern in your changes, I just don't see the logic behind it.

GW clearly designed TS as 1) Sorcerers, 2) bodyguards, and 3) minor vehicle support.

What is the problem with that thematic vision?

1) You still have the option for 3 Command Choices, and multiple Sorcerers in either Core. Maybe make it 4 Command Choices per Core, 4. Auxiliaries per core?
2) The War Cabal is pure Psykers and the Sekhmet Conclave can be run as such. Plus any Mark of Tzeentch character can purchase a Mastery Level. With Blessing Of Tzeentch letting you adjust Lore of Tzeentch rolls by +-1, you have a 50% chance of Doombolt, a 50% chance of Webwarp, and a 33% chance of Treason, while Tzeentch's Firestorm no longer sucks. The War Coven circumvents normal rules altogether, and allows for a lot of shenanigans based on which Cult you take the formation for. You're not just taking Chosen, you're taking Chosen with Brotherhood of Sorcerers that ignore the original restriction of generating a power from Lore of Tzeentch (but they would still get Firestorm due to Chaos Psychic Focus). Then you get other shenanigans, like Scouting Twistbray casters, so you could Outflank, deliver a Doombolt, then be Web warped by another friendly caster to safety.
3) The Apostle can be a caster as mentioned. He also loans his Leadership, letting Tzaangor blobs have an even easier time with getting Bestial Fury off (plus it avoids the awkward of the current Warherd where only the Tzaangors get to Run & Charge, so adding any character to them for better Leadership removes that option). In a pinch, you can combine Beseech with the better Boon of Mutation.

Basically, I'm interested in the Coven allowing for a core playstyle that rewards multiple small casters over a few big ones (otherwise, you get lists like Magnus & Friends), and allows for more variety within that besides "replace the free spell from the Cyclopea Cabal with conditional harnessing Warp Charge on 3+".

I might still do more tweaks, like making the ML 1 Psyker upgrade mandatory for characters with Veterans of the Long War, or tweaking the War Coven "secondary boons" (Interceptor for Telepathy is probably a bit too good for example; come to think of it, replacing it with Adamantium Will would make more sense).

My understanding is that TS are a faction where the majority of the legion was turned to dust. The only survivors are Sorcerers turned up to 11, who tend towards individual agendas.

The problem with a Brotherhood of Psykers unit is that it's in contradiction to the core themes of the TS. Most of those Chosen models should be dust. Meanwhile, your Sorcerers are supposed to be rare, independent, and certainly not expendable. When you have 5 or more non-character psykers in a unit and they cost about 20pts each, it communicates the opposite.

Next question -- why did GW neglect to add any vehicle formations? Fluff reasons! "The Thousand Sons show markedly little interest in properly maintaining their traditional armoury, these repurposed goods never last long and certainly do not appear in large numbers". Once again, you are going in the exact opposite direction.

I think your desire to write unique rules and expand options has a fatal dilemma. Thematically, TS are very tightly focused. There's only so much you can add until it starts to offend against the fluff. Did the Thousand Sons actually have any Warpsmiths or Apostles in their legion? This is probably the reason you can't take them in their unique detachment, and adding a ML doesn't change the fact that they don't really belong in the first place.

Thematically, the core of Thousand Sons is that most their soldiers are dust, while the rest are powerful casters. They supplement themselves with large numbers of auxiliaries, and some Daemonforge tools and Tzeentchian Daemons. Whether there are Sorcerer cabals that preserve elements of the Prosperine Cult structure is left ambiguous, as well as the fates of the Hidden Ones, the Spireguard (doesn't mean they shouldn't be an option, ex: reenact Battle of the Fang, etc).

1) In the Pete Haines codex, Chosen and Terminators were the same unit, and 1 model could be a Psyker; 1k Sons Possessed could also be an entire unit of Psykers too. For thousand sons, any number of models could become Psykers instead. 30k Thousand Sons are also coming out via HH: Inferno, with the option to upgrade Legion Veteran Tacsquads and Terminator squads with Brotherhood of Psykers.

2) And yet by RAW, you could technically make a 1k Sons Grand Coven which is 2 Sorcerers, 1 Rubric Marine unit, 1 Scarab Occult Terminator unit, and 17 unupgraded Predators for 1850 points. Not that you would because it would be a terrible list, but you could legally do that (or 10 Maulerfiends/Vindicators, because why not?). I dunno about you but something seems a bit...off about that. (Maybe add a "3 Auxiliaries per core" cap or so?)

In either case, I fee it makes more sense to emphasize Daemontech for Thousand Sons more than the conventional vehicles; they have the prowess to "control" the worst of their mutations after all.

I had a few additional tweaks/thoughts accordingly:
-War Cabal: Remove the part in Arcane Assault about Forge/Maulerfiends being ML 1 Psykers. Add a new rule: Arcane Conduit: After selecting a Psychic Power to manifest but before rolling to harness Warp Charge, a Psyker from the War Cabal may nominate a model from the same formation within 12" with the Daemonforge special rule to be an Arcane Conduit. The Arcane Conduit is considered the point of origin for the Psychic Power; a model may only serve as a Conduit once per turn.

-Make the "extra" ML +15 points instead of +25. ML 1 is ML 1 after all. Make it a mandatory upgrade for characters with Veterans of the Long War.
-Making the Warband an auxiliary rather than a core is intentional. Obsec is powerful. Obsec and Psychic Ritual is potentially very powerful. You require a minimum of 3 Rubric Marines and 2 Marine units with Mark of Tzeentch to pull off such shenanigans though. It's "possible" but not recommended.
-Redo the bonus for Defilers in Spireguard Besiegers. A Defiler within 9" of a unit of Cultists from the same formation may elect to re-roll any dice. For each die rerolled in this manner, remove d3 cultists from that unit, starting with those closest to the Defiler.