[@Roosan] Actually, Tyranids are apparently completely immune to Chaos fuckery due to how the Shadow in the Warp works, i.e. basically Warp static, which is why Warp travel near a Tyranid fleet is impossible, and why all the psykers on a planet die horribly prior to an invasion. If they invaded the galaxy full-force, they'd probably [i]drown[/i] the Chaos Gods outright. Or the equivalent of that, anyway. In any case, [url=http://wh40k.lexicanum.com/wiki/Octarius_War]the Octarius War is definitely a thing that happened/is happening in canon.[/url]