Another concept/sketch batch I have been sitting on for a while, suppose I could toss this out into the aether now haha
Basically it's a whole chaos space marine warband based around mimicry and infiltration - they look like a suspiciously normal space marine chapter from the outside but OOPS! It's all mimics.
(And not just the space marines/power armor, but everything is game: crew fused with their vehicles, transforming weapon "familiars," etc. It gets silly.)
They stem from the Raven Guard but can end up anywhere, and will take on the colors/appearance necessary to pass undetected. there is a catch though: their presence has a tendency to cause things around them to start to warp and glitch and in extreme cases, essentially cause little warp micro-rifts that end up mimic-ifyng things around them - so they pretty much have to operate solo to have the best chance at keeping their disguise up.
This CAN work to their advantage though if they are attacking in full-force as a warband, and some older members might have fallen too far to Chaos to keep up a normal "shell" anymore, so the overly mutated fellows have to be put to different uses
(in fact, there a degree of hierarchy of mutation stages that influences how they organize themselves as a warband & determines everyone's primary functions. And it's not really one over the other either - there are not all that many of them, so they have more luck spreading their influence clandestinely versus relying on brute force of any kind, that would have to be for emergencies. So, some of the more senior & mutated fellows might be more powerful on a physical/psychic level, but it is also like a forced retirement from their infiltration role, so it limits what they can do to further the warband's interests.)
SUMMARY: In a remote military outpost in the 19th century, Captain John Boyd and his regiment embark on a rescue mission which takes a dark turn when they are ambushed by a sadistic cannibal.
One of my favourite strike backs at nitpicking is the creator commentary during X-Men 2, when Storm asks if Mystique can shut down the copy of Cerebro from the control room and Mystique simply, bluntly, tiredly says "No." The creators confirmed that they specifically put that moment in to quell any viewers moaning about why the characters don't simply shut down the machine; by stating quite clearly, in-universe, that they can't turn it off. I love it.