A MUTANT! Or maybe a stable one, like an abhuman. A felinid, perhaps? But fully capable of speech, and without any weird yowling or other strange behavior. He blinks, looking into the mismatched eyes with his own grey ones.

"If these weapons are so poorly made a bit of pressure from the hand of an Astartes can shatter them, they clearly weren't planning well." You know, nevermind the fact he can probably crush tank armor.