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 Hlaine Larkin mk2 wrote:
In one fo the caphias Cain novels when Jurgen - a blank- (I think that's the adjutant's name) approaches a synapse Tyranid it inflicts pain on the bug.

it could be that the Hive Mind uses the warp to communicate (Like subspace is used in B5) and a blank cuts them off from that connection

Actually, Jurgen disrupted Tyranid synapse in several of the Cain books. Not sure if this was because the author had started down a path with that over 10 years ago or if there is simply a difference between BL and the codex fluff dealing with the warp and nids.

Ah I see, I've only read the one Caphias Cain novel, didn't realise it was a recurring thing in the series

Dunklezahn wrote:Narvhals cause massive tectonic upheaval and Nids can spawn whatever they need. They could spawn a fleet of them and point them at Terra. Biomass wise it's a drop in the ocean but it could devestate the planet without sending your troops anywhere near. The blow to Imperial morale seeing large parts of Terra in ruins...

Actually we have no idea how much tectonic upheaval Narvhals cause, and neither do we know if more than one can 'target' the same planet.

 Brother Captain Alexander wrote:

This was retconned by 5'th edition Necron codex fluff. Not only that Necrons ships are slower than Tau ships ( they literally need decades to reach nearest star system ) but Imotechs entire space armada was defeated by Black Templar strike fleet. The text even says that Necron ships were fleeing from Space Marine ships that destroyed them mercilessly.
Giving this incident the Necrons simply don't posses power to stand against Imperial Navy battlegroups ( who are much, much stronger than Space Marine ones ) and they cannot just "pop up" near Mars because they don't have their fast FTL anymore.
So Necron Mars raid from 3'rd edition codex edition never happened.

It is never stated in the Necron Codex how slow Necron ships are or the time it would take them to travel without the Webway. The size of the fleet Imotekh was using is unknown (it's unlikely it was his entire fleet because then he wouldn't remain a threat). But yes, it does seem to change the power of Necron vessels. In regards to the incident at Mars, they could "pop up" at Mars because they can use the Webway to travel. While we don't know if it has entrances in or near the solar system of Terra, it still allows for the Mars incident to occur.

Furthermore, considering the Necrons waged a galaxy-wide war against the Old Ones and their creations and were winning before they breached the Webway with Dolmen Gates, it's logical to assume that they still have some sort of FTL.

Sir Pseudonymous wrote:The tyranids so far have inflicted only the lightest damage on the Imperium, and have time and again collapsed in the face of all but the very lightest and haphazard defenses.

The Tyranids did manage to take Gryphonne IV though, supposedly the second greatest Forgeworld (coincidently just mentioned) in the Imperium. The text reads like a single Tyranid organism managed to take out a Titan Legion, unlikely though it is that the other Tyranids wouldn't engage at the same time. That one creature (a Tyrannofex maybe?) would be indestructible against most opposition.

SomeRandomEvilGuy wrote:

It is never stated in the Necron Codex how slow Necron ships are or the time it would take them to travel without the Webway.

Wrong, Necron codex page 8, the entry for Dolmen Gates.

The size of the fleet Imotekh was using is unknown (it's unlikely it was his entire fleet because then he wouldn't remain a threat). But yes, it does seem to change the power of Necron vessels. In regards to the incident at Mars, they could "pop up" at Mars because they can use the Webway to travel. While we don't know if it has entrances in or near the solar system of Terra, it still allows for the Mars incident to occur.

It's is his persona battleship so he must had some serious fleet guarding him ( not his entire armada, but I would assume the fleet of large size giving his position as leader of his dynasty ), if Space Marine fleet can go trough that then Imperial Navy can win them every day of the week. The Mars incident happened when several Necron ship just appeared in front of Mars Fleet and ignore it while landing on the surface of the planet, with their present FTL that is not possible and giving into account the incident with BT fleet Mars fleet would vaporize them before they touch the planet.

Furthermore, considering the Necrons waged a galaxy-wide war against the Old Ones and their creations and were winning before they breached the Webway with Dolmen Gates, it's logical to assume that they still have some sort of FTL.

It's painfully slow, read the paragraph that I offered. The text says "slow-voyaging ships stasis ships, dooming them to isolation". That sounds like FTL more slower or as slow as Tau one.

Sir Pseudonymous wrote:
The Tyranids did manage to take Gryphonne IV though, supposedly the second greatest Forgeworld (coincidently just mentioned) in the Imperium. The text reads like a single Tyranid organism managed to take out a Titan Legion, unlikely though it is that the other Tyranids wouldn't engage at the same time. That one creature (a Tyrannofex maybe?) would be indestructible against most opposition.

I really hope we will get explanation for this in their new codex or anywhere in future. Cruddance wrote it so the man maybe get little ahead of himself ( like saying that the Leviathan is the last big Hive Fleet out there ).

You dont get your ''The emperor did it'' card against the tyranids. IF we are to assume that the tyrandis get to the terra in force then the shadow will be undennyable. Then at least a good half of all the psykers in the astra telepathica go insane, die or explode. Astropaths couldn't co-ordinate the defense, i wonder if the imperium still has cell phones??? And with most of the psykers dead, who feeds the emperor? No new psykers coming in system, all the tyranids need to do is keep the shadow goign untill they run out psykers to feed the big E, and as i understand it something bad happens. Not sure if he dies, but he will be in no conditition to blow the tyrandis away.

Defenses can be over-came. You say that lunar took out 1/3 of the traitor fleet? Now imagin a fleet probabilly a hundred times bigger, maybe more. Still confident that they can take them ALL out before they make planet fall? Tyranids do indeed have anti titian bio titians which by the writing took out titian legions on its own. Also presumably Zoanthropes are some of the most powerful psykers around (floating, forcefielded, warplancing MoFo's they are) and there would be thousands of them. What extra damage just they could do would be catastropic, even if they are delagated to just making sure no reinforcments come through. Tyranids havea counter to everything the imperium has to offer, or at least a way around it.

what's the possibility of the nids just sending a decoy at Terra drawing all the forces away, possibly something like what the Allies did on D-Day with a bunch of empty wooden boats, maybe a bunch of empty bio ships. I dunno

SomeRandomEvilGuy wrote:

The Tyranids did manage to take Gryphonne IV though, supposedly the second greatest Forgeworld (coincidently just mentioned) in the Imperium. The text reads like a single Tyranid organism managed to take out a Titan Legion, unlikely though it is that the other Tyranids wouldn't engage at the same time. That one creature (a Tyrannofex maybe?) would be indestructible against most opposition.

I thought it said something about bio-titans, which would mean hierophants, which are/were ridiculously OP gargantuans (it costs less than a reaver, has ten wounds at t9, a 2+ armor save, and an invuln that is either 3++ or 5++ (I don't know if this was ever officially resolved, it stemmed from it having a power that, when its book was written, gave a 5++, but in the 5th ed tyranid codex that changed to a 3++), and two s10 assault 8 weapons with 48" ranges).

Of course, that particular bit is rather out of place with the tyranids' normal portrayal, since if they could just up and drop completely invincible super-weapons into the fray whenever they came up against something that could fight back, and could defeat near-space-marine-strength forces fielded in guard-like numbers, they wouldn't lose whenever the guard could show up in time to fight them...

 ALEXisAWESOME wrote:
You dont get your ''The emperor did it'' card against the tyranids. IF we are to assume that the tyrandis get to the terra in force then the shadow will be undennyable. Then at least a good half of all the psykers in the astra telepathica go insane, die or explode. Astropaths couldn't co-ordinate the defense, i wonder if the imperium still has cell phones??? And with most of the psykers dead, who feeds the emperor? No new psykers coming in system, all the tyranids need to do is keep the shadow goign untill they run out psykers to feed the big E, and as i understand it something bad happens. Not sure if he dies, but he will be in no conditition to blow the tyrandis away.

Defenses can be over-came. You say that lunar took out 1/3 of the traitor fleet? Now imagin a fleet probabilly a hundred times bigger, maybe more. Still confident that they can take them ALL out before they make planet fall? Tyranids do indeed have anti titian bio titians which by the writing took out titian legions on its own. Also presumably Zoanthropes are some of the most powerful psykers around (floating, forcefielded, warplancing MoFo's they are) and there would be thousands of them. What extra damage just they could do would be catastropic, even if they are delagated to just making sure no reinforcments come through. Tyranids havea counter to everything the imperium has to offer, or at least a way around it.

You likewise don't get your "The Shadow In the Warp stops all psykers!" card, because the Shadow has never tried to directly tangle with the God-Emperor. For all we know, all the brain-bugs explode into purple and green goo once they pass Pluto, leaving the fleet to turn on itself in a frenzied orgy of ravenous hunger.

A thousand psykers (the weakest of them) are fed to the God-Emperor a day in order to power the Astronomican. The Astronomican is not powered directly by Him, as it existed before He ascended to the Golden Throne. He simply points it, kinda like a lighthouse. Lacking the Astronomican does not make Warp travel impossible, just more difficult.

Cell phones? Cellphones exist, though its not possible to use one at inter-planetary distances at any sort of reasonable speed.

The defenses of the Sol system have increased exponentially since the time of the Heresy. Coupled with the relatively slow in-system speeds of the Tyranid, this means that the Hive Fleet can be effectively bottle-necked between the orbits of various planets, and thus taking fire from the Imperial fleets in space as well as the planetary defense stations around those planets (like, say, Saturn and Jupiter, not to mention the asteroid ring), long before any of its ground forces can be deployed.

 Shlazaor wrote:

1. The Emperor might not be able to stop the shadow in some other system but you can bet your ass he can stop that gak in the Sol system. The Emperor literally gaks psychic weapons. Come at Terra Hivemind.

I highly doubt the Emperor "gaks psychic weapons" unless the fluffs changed from the last time i read it, does the big E not need thousands upon thousands of psykers to be sacrificed a day just so he can wheeze a bit more.

If it was 4th gen tyranids with the 5gen creatures added in it would be highly in the favour for the nids, but i believe it was MGS that mentioned it earlier in the thread that with the nids 5th ed codex they did take some stupid nerf bat hits for their fluff so they have to many cons outweighing the pros in their favour.

In honesty i think the Emperium would win but at such a cost that it would not recover in time for somebody like the orks or chaos to wipe them out afterwards. And looking over some of the other people posting about the void dragon have raised some interesting points aswell.

Needless to say if the nids do get to Terra it could pretty much end half the factions in the 40k universe just from the aftermath and i dont think GW would do that unless they wanted to make orks or daemons their new poster childs

I highly doubt the Emperor "gaks psychic weapons" unless the fluffs changed from the last time i read it, does the big E not need thousands upon thousands of psykers to be sacrificed a day just so he can wheeze a bit more.

He... kinda does. The payload for psybolt ammunition carried by the GK is made from biological effluviant from the Golden Throne. Make of that what you will.

Huh did not know that one....... The more you know eh

edit: and as a thought, I guess they just pump the big E full of laxatives and mexican food then

starchild... ynnead... Would the eldar not sacrifice themselves to stop chaos? assuming the emperors power comes from pyskers, the eldar races souls would "charge him", and so if he were to die, the resulting entiity would be a very powerful...

a b3ached whal3 wrote:
starchild... ynnead... Would the eldar not sacrifice themselves to stop chaos? assuming the emperors power comes from pyskers, the eldar races souls would "charge him", and so if he were to die, the resulting entiity would be a very powerful...

Or...... He would just be dead

 ALEXisAWESOME wrote:
Why wouldn't the shadow in the warp over come the astrominicion?

The answer is that it would block out the astronomicon, or at the very least severely distort it. Apparently a flicker in the astronomicon causes massive losses across the whole of the Imperium. A Tyranid attack would wreck the Imperium for good. The shadow in the warp shows up weeks before the Hive fleet even appears and this would in turn render all warp travel impossible.

The Tyranid attack on Terra would depend on the size of the Hive fleet. Behemoth was a small Hive fleet and the Ultra marines had weeks to prepare their defence. Macragge being one of the toughest nuts to crack in the whole galaxy. A large Hive fleet such as one of the tendrils of Leviathan would devaste Terra. The Tyranids would use up huge amounts of energy in their attack, however they would rapidly begin to replenish that lost energy as the feeding and reproduction stage of the infestation started.

The defenders of Terra would starve quickly. The Terran system produces nothing, all it's food and resources must be brought in, even Mars needs raw materials o brought in for any work to be done as all of Terra's resources were stripped long ago. A Tyranid attack would result in rapid mass starvation and a total collapse of order as no food or supplies could reach Terra due to the shadow in the warp.

The problem with debating anything about the Tyranids on a larger scale is we simply don't have much information about them, and the information we do have varies greatly from source to source (and even sometimes, like Cruddace, varies from the same source).

For example, when people picture a hive fleet, I get the impression they think of it as a few dozen bioships moving in regular fleet formation. Fluff in Battlefleet Gothic suggests an average fleet tendril numbers in the millions of hive ships, not counting the support and combat ships, and artwork supports this (it's more like a living wave in space). Not to mention Battlefleet Gothics fluff makes it literally impossible to beat them in a naval engagments (Imperial weapons stopped working after 3 engagments as the Tyranids developed resistances to Imperial technology), yet we have them being beaten in naval engagments.

We've got fluff concerning the Hive Mind sitting in the warp, and we've got fluff saying the Tyranids don't make use of the warp (thanks Cruddace). We've got fluff saying Tyranids, even leader beasts, are slaves to the Hive Mind, synapse creatures basically being like wireless routers with lesser creatures connected to it. We've got fluff saying the leader beasts actually have glimmers of self awareness and the ability to think for themselves (thanks Cruddace).

So you basically need to 'read between the lines' with Tyranid fluff.

We've got fluff that says they go after worlds their vanguards get established on enough to project a psychic beacon, and we also have fluff supporting the fact that they think strategically and don't simply go for the juicy worlds right away. Jormungandr awoke, saw a juicy target, but spent decades feeding on the outer system planets until it was strong enough to attack. Leviathan hit Gryphonne IV, a Forgeworld. As we well know, Forgeworlds aren't known to have very active biospheres, so a Tyranid Vanguard wouldn't really be able to establish itself. Which further points to why they would have attacked it - quite simple, they know the galaxies prime defenders success is in part due to the importance of these 'factory worlds', so taking one out would make it easier to attack other planets in the region.

Octarius is often brought up, but as it says in the fluff, neither side is losing, and both sides are getting stronger. Further fluff has the Swarmlord systematically killing Warlords and destabilising the defenses. Before the Swarmlord even showed up, they gained a foothold in the system by killing Skarfang, by luring him into a trap consisting of Venomthropes to cloud the area and Lictors to assassinate him and his bodyguard. Another sign of tactical thinking.

Even the spark that started this thread, the Tyranids being attracted to Terra by the Astronomican, makes sense given older fluff, but Cruddace simply didn't bother explaining why. Going by established fluff, Tyranids are attracted to worlds by the psychic beacon projected by their Vanguard (Genetsealers and Lictors), which is stronger depending on how well esteblished they are. The Astronomican is basically a huge buffet sign, so the Tyranids are seeing it, and want to go there.

Given the fact that they can think strategically, even if they reached it and found the ridiculously big defense fleet there, they'd lose a hive fleet, back off, and start thinking again. Is it worth even trying to attack? That's a mighty big sign, but it's also an even greater risk.

It's more likely that after an initial wholloping by Sols defenses, they'd go back to simply eating everything else. Those defenses are coming from somewhere, so destroy that first. Eventually, those defenders will be drawn out peicemeal to defend needed resources, where they can be taken down peicemeal.

Something to remember is that GW often forgets that Tyranids really don't make sense - the fact they eat so much means it's likely due to them needing to eat, but they have no problems making Tyranids great 'long game' thinkers.They're trillions of years old by now as a race, and the Hive Mind itself is as old as the race. It's intelligent, thinks strategically, and knows how to wait.

If the Tyranids ever got the strength to reach Terra-which they will not- then they would have the strength to take Terra.


Automatically Appended Next Post:
But like Loki said, the whole situation is very unlikely.

 ALEXisAWESOME wrote:
Why wouldn't the shadow in the warp over come the astrominicion? Especially if there were enougth tyranids to feasibly be a threat to the terra. Neither of us have any sources to prove our claims, as i dont believe anyone has tryed to block the astromincion before. But we know that tyranids can block psycik powers and block out the astrominicion. So if we conclude that it is like throwing a blanket of a system, well you can throw a blanket over a light bulb to block out the light to the room, or you can put the blanket over an area of the room to blovk out the light to there. Does that make sense or am i crazy? Well im not, my mother had me tested

This means that a huge amount of imperial troops would be lost in the warp, any many of the chapters. Its quite possible that the entire grey knights chapter heads would explode because of the massive shadow, and even if they dont they're psykic powers would be both dangerous and dampened. Also the seer amount of Navhals arriving in system would create LOADS of natural destasters, earthquakes, volcanoes ( which mars is riddled with) and tsunami's across the system. The shadow also means effective communication between ships is impossible.

In other words the tyranids are bouncing on the shadow doing most of there work for them. Lazy tyranids

I don't know where you're getting your fluff from, but you've got the wrong end of the stick about most of this. For each point, I've included book sources - all of them well worth a read!

The natural disasters thing has no basis in anything, plus most of the planets and moons would be entirely unaffected as they're inert, gas giants or the only areas in use are orbital platforms. Martian volcanoes have been dead millions, possibly billions, of years. (See Horus Heresy books, plus The Emperor's Gift, Inquisiton War....)

The Shadow in the Warp doesn't affect psyker powers in the same way that pariahs or Eldar runes do, what it does do is block the Astronomicon and astropathic communications.

It doesn't do this by power or force, merely by being a conglomeration of so many voices and creatures that it drowns out others. It's not an explosion or wave, it's more like the phone lines are jammed... (See Warriors of Ultramar)

It also doesn't block in-system communication as this is technological, rather than psyker-based. Read the Word Bearers books for a fantastic illustration of exactly what happens when all warp and psker activity is shut down in an entire star system. It doesn't cripple anything, It slows things down, and psykers can't use their powers, but they don't die or explode. (See Dark Creed)

As for whether it would block out the Astronomicon signal, nobody can guess. The Shadow was blocked it out before, but only on the far sides of the galaxy. The Emperor is incredibly powerful, though, so it may not be enough. (See Thousand Sons)

And, of course, the Terran system is without any doubt the most heavily defended, armed and powerful region bar none. And there would be a lot of warning that the Tyranids were coming - as the shadow they cast can be detected in the Warp over many months and even years (see Caiphas Cain books)

Anyway, the Orks are totally gonna stomp 'em....

</controvercial>

Go orky waaagh . Stomp those bugs. Then die an explosive deaths.

 Brother Captain Alexander wrote:

BlaxicanX wrote:
The day the Tyranids get to Terra is the day the Tyranid species goes extinct.

This.

Terra is the most heavily defended planet in the Imperium. Not just Terra - entire Sol System is fortress that makes Cadia look like a little baby in comparison.

...so seure that entire Necron fleets manage to get down to Mars without humans even noticing. Ehem.

 Sigvatr wrote:

...so seure that entire Necron fleets manage to get down to Mars without humans even noticing. Ehem.

That was retconed, Ward write off 'magic FTL' and Necron fleet strenght. Without those two elements Mars raid is impossible to happen.

It's one of those unfortunate situations where he didn't retcon the event, just the technology used to make it happen. So it's left in a weird state of having happened, but the only way for it to have happened is the Imperium was completely stupid and let it happen, rather than the Necrons being so technologically advanced they managed to break the blockade.

I'm fine with the new explaination.

 -Loki- wrote:
It's one of those unfortunate situations where he didn't retcon the event, just the technology used to make it happen. So it's left in a weird state of having happened, but the only way for it to have happened is the Imperium was completely stupid and let it happen, rather than the Necrons being so technologically advanced they managed to break the blockade.

I'm fine with the new explaination.

This is one of those situations where we can use logic. I completely agree that a lot of this is subjective but there is a point where can reach conclusions as rational individuals without having GW spell it out for us.

 Shlazaor wrote:

 -Loki- wrote:
It's one of those unfortunate situations where he didn't retcon the event, just the technology used to make it happen. So it's left in a weird state of having happened, but the only way for it to have happened is the Imperium was completely stupid and let it happen, rather than the Necrons being so technologically advanced they managed to break the blockade.

I'm fine with the new explaination.

This is one of those situations where we can use logic. I completely agree that a lot of this is subjective but there is a point where can reach conclusions as rational individuals without having GW spell it out for us.

Rational decisions about 40k fluff doesn't work, because a lot of decisions they make themselves concerning it are not rational (like claiming an entire race was destroyed because one of their planets was eaten by Hive Fleet Kraken - real rational).

The general rule with 40k fluff is, unless outright refuted with new fluff, it still happened. They changed Necron drive technology, but they could have still landed on Mars another way. Since Ward didn't bother correcting that bit of fluff, like all 40k fluff, it's assumed it still happened.

Even if they don't have super-FTL drives, there's nothing saying that a ship cannot carry a previously-unrevealed Dolmen Gate-creating device that allows them to pop up in various places in the galaxy, even if said device does not permit unlimited travel, or has to "lock in" on pre-set frequencies, co-ordinates or whatever.

That the Necrons have some means of detecting a C'Tan Shard that "goes active" in some way is not really too far-fetched a concept.

 -Loki- wrote:

 Shlazaor wrote:

 -Loki- wrote:
It's one of those unfortunate situations where he didn't retcon the event, just the technology used to make it happen. So it's left in a weird state of having happened, but the only way for it to have happened is the Imperium was completely stupid and let it happen, rather than the Necrons being so technologically advanced they managed to break the blockade.

I'm fine with the new explaination.

This is one of those situations where we can use logic. I completely agree that a lot of this is subjective but there is a point where can reach conclusions as rational individuals without having GW spell it out for us.

Rational decisions about 40k fluff doesn't work, because a lot of decisions they make themselves concerning it are not rational (like claiming an entire race was destroyed because one of their planets was eaten by Hive Fleet Kraken - real rational).

The general rule with 40k fluff is, unless outright refuted with new fluff, it still happened. They changed Necron drive technology, but they could have still landed on Mars another way. Since Ward didn't bother correcting that bit of fluff, like all 40k fluff, it's assumed it still happened.

Unless it contradicts related fluff. The Necron fleet was assbeat by a Space Marine fleet. The defenses of Mars would be a thousandfold stronger. I reject your base assumption that we cannot rule something out even if it is not straight out retconned.

Can we claim the event still happened via Dolmen Gate? Sure. It's subjective. But we can confidently say that a few Necron ships did not circumvent the entire Mars orbital defense and land on the planet.

clively wrote:

 Hlaine Larkin mk2 wrote:
In one fo the caphias Cain novels when Jurgen - a blank- (I think that's the adjutant's name) approaches a synapse Tyranid it inflicts pain on the bug.

it could be that the Hive Mind uses the warp to communicate (Like subspace is used in B5) and a blank cuts them off from that connection

Actually, Jurgen disrupted Tyranid synapse in several of the Cain books. Not sure if this was because the author had started down a path with that over 10 years ago or if there is simply a difference between BL and the codex fluff dealing with the warp and nids.

Just for clarity here, in Amberly's notes in Duty Calls, she states outright that neither she, nor anyone else, was ever able to say with certainty that Jurgen was able to actually block out the Tyranid Hive Mind. The instance you mention shows a blank at least makes psychic communication between the Tyranids difficult, but it certainly didn't "cut them off". There are also plenty of instances of Jurgen standing right next to different Synapse Tyranids (two Hive Tyrants, one after the other) and he had no noticeable effect. Perhaps because a Tyrant has a more powerful mind that a Warrior? Who knows.

The only thing I can say about this is:

'NIDS+SOL SECTOR= find a chair, sit, grab the popcorn and get ready for Epic.

Tyranids attacking the Terran system could have a much wider effect.

Chao's will see an opening and launch another Crusade at Cadia, weakening the Imperium.
Eldar and possibly even Dark Eldar will recognise that if the Imperium falls then they are next, and so will probably give their help.
Who knows what the Tau will do? Offer their help if the Imperium see's the Greater Good?
Necron's may even aid the Imperium.

 phantommaster wrote:
Tyranids attacking the Terran system could have a much wider effect.

Chao's will see an opening and launch another Crusade at Cadia, weakening the Imperium.
Eldar and possibly even Dark Eldar will recognise that if the Imperium falls then they are next, and so will probably give their help.
Who knows what the Tau will do? Offer their help if the Imperium see's the Greater Good?
Necron's may even aid the Imperium.

The Tau would be too far away from the Sol system with their non existent FTL

Orks would also join in fur da crumpin' da bugs and oomies

Everybody in this discussion go to page 409 of your basic rule book and look at the bottom right hand corner of how big the Tyranid fleets compared to the milky way galaxy. Do you even realize the distances involved from one star system to the next?

The artwork for the Tyranids has them being so massive that thier beginning fleets cover massive distances with nothing but ships full of tyranids. Their numbers are super massive. The Imperium in one system does not have enough firepower to stop all of that. Remember, it only takes one tyranid ship crash landing on planet earth to start consuming it, So as it gets blown away, as happened in the Battle for Macragge, it crashes on the planet and the tyranid creatures on board survive and start to eat the inhabitants of the planet.

It is known fluff that the Shadow in the Warp directly blocks the Astronomicon, causing psykers of all levels to go insane and commit suicide or die or any number of other things.

It was so powerful that it blocked Iyanden from recieving much help at all from other Eldar and blocked astropathic transmissions completely from Macragge. If the entirety of what you see on page 409 worked its way to Terra there would be nothing stopping them. Not the terran defenses, not the Eldar, not the orks, nothing. There are just too many of them.