Yeah, outside the walls. I want to move it for two reasons:
1. FBs don't belong in hell
2. I don't want the demons to kill it, get a name, and wander off
So I plonked it down in the third cavern to kill some creeping eyes. It killed 5-6 before being killed itself. I forgot to mention, it's a salt quadruped with special attack. So I'm sending one of my untitled military dwarves to go kill it. The rest were killed by some haulers. There was only one injury, a bone carver threw a creeping eye into himself and broke his hand on the ground. The speardwarf, who was not far, killed the offending creeping eye.
Something to note - Over half my fort is legendary at something. This makes them tough as nails with the personalities to match, most don't care about anything anymore and will beat the shit out of any cavern dweller stupid enough to fuck with them. My baron has a jabberer kill under his belt and the Brewmeister has killed a GCS with a single punch to the head. Many more have lesser kills.
That isn't to say my dwarves are unhappy - I haven't seen stress over 10k in decades.
As for my greatest enemy? FPS. I'm chugging along at a nice 4 right now. All other enemies have been eliminated. My military crushes all external threats with ease. Forgotten beasts are trophies to be captured, not threats to be feared. My dwarves walk unprotected through hell without fear. The only thing that could possibly threaten me is a flying webber titan - and I killed the only one.