[Haunted Evil Pajamas]

I have a mutated Kirosh, which is normally a sword, but mutated into a gun.
While I can do most of what I want with it, I cannot seem to use Warning Shot with it, the skill is simply grayed out.

Also can you explain to me in detail what the Kirosh's ability is, "field tiles being unaffected by movement," last I tried I walked on cinder tiles and they still roasted my feet?