Xeno symbiotic

You wake from a concussion. a frag grenade threw you across the hall into a room. the system's purging protocol scorched the hall and everything in it. both trooper and xenos alike. A xenos population capable of mimicking objects no matter its condition waits in hiding in every corner. its killed over thousands of your regiment. these xenos vary in size and aggression. thankfully your lasgun can kill them. you have 200 shots left out of 10000. make them count. and in the grimdark future of warhammer 40k every shot must count.