[Joe]

I like it. I'd be tempted to say that Dungeon Demons feed on souls rather than bodies, just to explain why they go to all the trouble of preying on people. If they just want calories, then there's much easier prey around!

Also, if they're after meat, then it's a bit more difficult to explain how they manage to pump out so many meaty monsters on such a regular basis. Thus to my mind it would be better to say that they're powered by sentient souls, which allows you to hand-wave the whole energy issue.

You could even say that they get more juice out of heroic souls, which is why they sometimes try to lure in really heroic types by capturing princesses etc.

This would also have the benefit of solving the "I decide to raise some dungeon demons of my own" problem. Anyone who decides to do that will have to feed the little baby dungeons, not just corpses, but living, sentient beings - which is definitely a good way to become corrupted, just as you say.