salvadorjer wrote:Very little sadly. Nids eat CSM since it's their primary drive. CSM fights nids for 2 reasons as far as i can tell, when it helps them take the fight to the imperium (such as if the nids are on a planet with a relic they need or are simply in the way). The other reason CSM fights tyranids is BLOOD FOR THE BLOOD GOD! (also many of them are insane so logic becomes a secondary concern).

...that is to say, unless everything you have been told is a lie...

Seb wrote:

salvadorjer wrote:Very little sadly. Nids eat CSM since it's their primary drive. CSM fights nids for 2 reasons as far as i can tell, when it helps them take the fight to the imperium (such as if the nids are on a planet with a relic they need or are simply in the way). The other reason CSM fights tyranids is BLOOD FOR THE BLOOD GOD! (also many of them are insane so logic becomes a secondary concern).

...that is to say, unless everything you have been told is a lie...

I'd add a third reason : CSM fight 'nids to defend themselves.

salvadorjer wrote:Not in the CSM codex or the Nid one (unless i'm blind). As for black library fluff i don't know the selection enough to give you a definitive answer there.

The codexes do have pictures of them fighting so it's assumes it happens, just not explained why.

Also in the adversairies section of the old GK book there were reasons for which the GK would fight the tyranids and explained things like tyranids being driven into a frenzy by a khornate artifact under a planet's surface that they are assimilating (yes i know it's not much of a change). Also there were cases of bio-ships being sucked into the warp and exiting completely mutated. It's possible therefore to imagine one stumbling upon a crone world or such, maybe even ending up in the eye of terror.

Fido198674 wrote:

salvadorjer wrote:Not in the CSM codex or the Nid one (unless i'm blind). As for black library fluff i don't know the selection enough to give you a definitive answer there.

The codexes do have pictures of them fighting so it's assumes it happens, just not explained why.

Also in the adversairies section of the old GK book there were reasons for which the GK would fight the tyranids and explained things like tyranids being driven into a frenzy by a khornate artifact under a planet's surface that they are assimilating (yes i know it's not much of a change). Also there were cases of bio-ships being sucked into the warp and exiting completely mutated. It's possible therefore to imagine one stumbling upon a crone world or such, maybe even ending up in the eye of terror.

Scary thought, a hive of nids being controlled by demons

The fortress world of Forgefane had been an Iron Warriors stronghold for millennia, ruled by Warsmith Kolvax and garrisoned by an entire Grand Company. The Iron Warriors are renowned siege masters and Forgefane boasted some of the most redoubtable fortifications conceived. Giant citadels and towering bastions jutted over the landscape, each protected by void shields and packed with enough ordnance to flatten a city. The land around each fortress was cleared for miles and a maze of razorwire, minefields and trenches guarded every approach. Obliterators patrolled every rampart and Chaos Titans stood watch over every gate. It was even whispered that Kolvax's Ironblood Citadel, Forgefane's greatest stronghold, rivalled Perturabo's Fortress of Hate on Medrengard in its defensive capabilities.

When Hive Fleet Leviathan wound its tendrils around the fortress world, the Iron Warriors welcomed the challenge, eager to test their latest defences and arrogant in the belief that all would perish at the walls of their mighty citadels. The initial attacks on the surface of Forgefane were costly indeed for the Tyranids. Swarms of Tyranids were vaporised by intense artillery barrages, and flak batteries shredded countless Gargoyles and Harridans. Not even Bio-Titans reached the bastion walls, cut down by Warp-powered lasers built into the sides of the Iron Warriors' citadels. But hte Hive Mind was quick to learn and soon adapted its tactics. The initial assault had exposed a single weakness in the Iron Warriors' defence, a chink through which Hive FLeet Leviathan could strike. The Iron Warriors continued their ceaseless bombardments, unaware that their true doom approached not from beyond their fortress walls, but from beneath them.

So it was that Hive Fleet Leviathan unleashed thousands upon thousands of Trygons onto the surface of Forgefane. Sheltered from the withering salvos of firepower on the surface, Tunnel Swarms quickly bypassed the IRon Warriors'defence lines and launched assaults within supposedly secure defensive perimeters. Subterranean Swarms quickly overran underground supply routes and despite many fierce tunnel fights the IRon Warriors were forced to pull back and seal them. Not even the Daemon Engines of Kolvax's Hellforge could withstand the Trygon onslaught. Talon and steel clashed in the foundries as over six hundred Defilers countered the assailing swarm, but for every Trygon slain, two more burst through the walls or the ground below. Within a few hours the Defilers were overrun. Cut off from their forges the Iron Warriors attempted to transport vital ammunition overland, but the armoured columns and supply convoys were ambushed by Bioshock Broods. One by one, Forgefane's citadels were overrun and soon only the Ironblood Citadel remained.

However of all the beasts that crawled beneath the surface of Forgefane, there was one that proved to be more deadly than any other. This monster could peel open plasteel bunkers as if they were made of parchment and eight bastions fell in as many days following its first sighting. In their need to find a focus for their hatred, the Iron Warriors named this treature the Tremorbeast, and with each massacre its reputation grew. The Warsmith, in his arrogance, resolved to slay the Tremorbeast personally - he was swallowed whole for his efforts, dragged into the creature's gullet by a writhing mass of tentacles. The Tremorbeast breached the Ironblood CItadel mere hours later, and as the Tyranid swarms poured through in its wake, the Iron Warriors knew that Forgefane was lost.

-Liber Apocalyptica: Trygons, WD 362