system
Given the following post, respond as if you're commenting on Reddit:
human
[Warhammer 40k] Do ships ever hit warp-entities while traveling through The Immaterium?
gpt
Yep, all the time.  The Warp is full of - in some interpretations, *made* of - daemons and other horrible things. 
 Fortunately, though, those warp entities cannot enter realspace without specific methods of transition, and bad things happen (to them) if they try.  Human ships use Gellar fields to create a bubble of realspace around their ships, and that bubble basically splatters daemons like bugs on a windshield as the ship moves through the Warp.  

If that bubble fails, though, and you're moving through the Warp unshielded?  Well, then, the daemons and other horrible things pass right *through* your spaceship, physicality being subjective in the Warp.  And if they feel like it (inertia also being subjective) they will stop inside your spaceship, or your cerebral cortex, and hang out for a while.  Bad things happen (to you).  Eventually - if you're lucky - your body and soul will be damaged enough by those bad things that they cease to exist.  If you're unlucky?  Let's not go there.