First thing about him is his rules. Set Warlord Trait, and his staf, and Fear.. 'Immortal Hubris' is great for that odd chance where our army wide LD 10 fails. Usually won't come up until you lose combat and don't want to get swept. Occasionally you'll come across a Harlequin player who will try to Death Jester you around, in which Szeras really shines because you have to fail 2x for him to start moving your army around. More common will be the odd Pinning test that you might fail, which will usually come in the form of Ordnance Barrage. His staff is a decent Tank Hunter for the first turn or two with decent range, and really handy to have in low point games. Do NOT forget fear. Against non-Marine armies, this thing will go off from time to time. They have to test EVERY turn now, and can really make some opponents get ready to flip a table.

The second thing is his RP bubble. All Crypteks grant the RP to the unit that they Join, but Szeras will grant it to surrounding units. The downside to this is the range, as you'll have to bunch up your guys or place them in lines. This is actually fine for the first turn or two as you approach your opponent because of the 24" range limitation of most of the Necron army. Just don't get caught in the trap of thinking that you have to keep them there the whole game. Don't be afraid to split your units up once they get in range to do damage, you'll only hurt yourself. Opponents will learn very quickly that shooting across your lines, or assaulting them will pull them out of range of Szeras and take away that bonus. Very useful for creating a CAD-Curion list where you grant the 4+ RP outside of taking a Decurion.

The last thing is his buff. Yes it is RNG-ish, but don't let anyone tell you that any of the options are bad, they all have their uses.

1 - +1T - This one is generally considered the 'best'. Having that bonus T isn't really that great when it comes to taking wounds as T5 is not uncommon. Where it shines is RP, since your opponents T8 won't penalize the RP. In lower point games, you won't find much ID that even the 5+ RP can't handle. In higher point games, I can see this being a valid point if you're NOT running a Decurion

2- +1 BS - Another one that I feel is great on lower point games, but on higher point games or with other combos it can potentially lose it's value. BS 5 is fantastic, especially in Low point games where you'll slide your average dice rolls enough to have a huge impact on the game. If there is a Triarch Stalker around, they get up'd to BS6, which means you get the odd re-roll from your 1's. The reason I think this is a drawback in higher point games, is that it's easy to have Zahndrekh choose the 'Target Priority' WL trait and just get straight BS re-roll on 1's instead of needing the 6's to follow up. It's also easy to get 'Preferred Enemy' into a unit to get the full BS re-roll and get the re-roll on 1's to wound, if you need it.

3- +1 S - I actually have come to LOVE this one, despite some Necron Players ignoring it as useless. More often than not, this buff has offset the slow initiative in CC and closed the gap on how much I lose combat by, or even winning combats. Doesn't seem like much until you remember that Szeras has 'Immortal Hubris'. All of a sudden your unit has become a quite effective Tarpit because of how hard they become to break. There is the potential to do the same thing as Wraiths and just Grind down and outlast your opponent in CC, really screwing up his plans.to just steamroll you. Also handy for assaulting most vehicles if you don't manage to Gauss it to death. It's amusing to get Pens on transports with Necrons.

The OTHER advantage, (and I've had it happen TWICE), is T8. S5 can wound T8 in CC. While you do need 6's to wound, an over confident Eldar Player won't really know what his Wraithknight is getting into. Just having the ability to put wounds on them in CC means that he might have to play a bit defensively if you knock a few wounds off of it with Gauss/Deathmarks. The usual strategy of ' I just need to make it into combat where you can't touch me' suddenly doesn't work. Again, combo'd with Szeras providing both the RP bonus and Immortal Hubris, this one can actually be another source of frustration for your opponent at any point level.

I just want to post here that you'll find it very common for most players to buff a unit of Immortals, it's easy to forget that he can also nominate a unit of Warriors. It makes sense since Immortals aren't as dependent on having a babysitter around, and having any of these buffs gives most opponents a real thorn to deal with. Especially if you have Anrakyr, or even Orikan/Obyron around in the unit.

Since Immortals are already a fairly independent unit, you should look at buffing a unit of Warriors. Since Szeras buff doesn't have a per model cost, you really see some mileage out of buffing a full unit of Warriors. 20 T5 Warriors with Szeras giving the RP bonus (and Immortal Hubris if it comes to that) is playing with an Immovable Object. 20 BS5 Warriors will provide more Gauss shots over the course of a game than a unit of Immortals will, and while I haven't done the math, I believe it offsets the loss of the AP 4 from the Immortals. It might even be an advantage against the 3+ armies. 20 S5 Warriors is a beast in CC, especially since any unit that gets close enough will rarely be at full strength by the time they get there, and survive Overwatch.

I experimented with some CAD's running 20 Warriors with both Zahndrekh and Szeras in the one unit. VERY effective, especially with Zahndrekh switching Warlord traits to accommodate whichever buff they get. He starts with Zealot, which i better than Immortal Hubris. Going Fearless with the T buff makes them a better Tarpit than even Wraiths, and I even used it to tie up 3 Dreadnoughts that I couldn't kill before they got to me for the rest of the game. Target Priority for the BS buff means that every shot is pretty much going to hit making the unit effectively twinlinked BS5. Get the S bonus? Implacable Conqueror and they gain Relentless/Crusader. The Myth that Necrons suck in CC really goes away when 20 Warriors roll up, Rapid Fire, then Charge with S5 Attacks (getting the Charge bonus). I promise you, no one will see it coming.

lluminor Szeras
3 x 16 Warriors (Szeras goes in the middle unit and gives the 4+ RP to all the units)
8 x Tesla Immortals (Tesla is an advantage here, because they're a rearguard unit that is behind everything else, usually sitting on an objective in my DZ. So they'll rarely see Rapid Fire for more than a Turn, and w/o Relentless in a Decurion, I like to have the option to assault)
5 Tomb Blades w/Particle Beamers, Nebuloscopes, and Shield Vanes (No subtlety here, they're in range of Szeras for the RP bonus if I don't go first, then they're off dropping Templates that Ignore cover or going after objectives)
20 Flayed Ones (LETHAL in this setup. Infiltrate in front of the Warriors providing a Cover save to the Warriors behind them, benefiting from Szeras RP until they get in range to murder anything that isn't T8.)

* Remember, all 3 Warrior units and Immortals are OBSEC in this list, so it's viable to kill your opponents Obsec and make him earn objectives.
** I DID originally have 1 unit of 20 and 2 units of 14 Warriors, but balanced it out a bit better to make all the Warrior units equally effective when they split up to cover more board. Personal preference, but both setups are good.
*** Drop 2-4 Infantry in any combination you like, and you can swap Szeras out for Zahndrekh, and you've got an equally brutal Decurion at 1250