Demon: Size 16 humanoid. Has wings and can fly. To fly just think of the sky as a giant staircase.
Flying is gimped in level terrain since the game only generates one sky level higher than the highest local ground level. This makes towns and mountains a good place to fly. Can't use their firebreath in adventure mode. [NO_DRINK], [NO_EAT], [NO_SLEEP] mean you don't have to take breaks or 'T'ravel constantly. Has a natural burn attack which is of note. A favored tactic is to bite chunks out of things then pelt other critters with those chunks.
Spirit of Fire: You're on fire. Size 11 humanoid, but don't even think of getting clothes to wear. You can kill things by just standing next to them long enough. Burning punch attack. Instantly turns any water that touches it to steam. Visiting glaciers is very interesting. Obviously can't swim so don't fall into any pools you can't travel away from. Well, that would be a problem if you couldn't fly. And you can. Has all the combat advantages a Bronze Colossus has as well as [SEVERONBREAKS] and [NO_EAT], [NO_DRINK], [NO_SLEEP]. Has a powerful burning punch attack.
Frog Demon: Size 12 humanoid. Can swim underwater without drowning, so you can go wrestle sharks if you can find any. [NO_DRINK], [NO_EAT], [NO_SLEEP] mean that you can actually get away with swimming across an ocean without major preparations. Strong natural bite attack, but it's not burning like Demons.
Tentacle Demon: Size 12 humanoid + 6 tentacles. Each tentacle has a claw on the end and can be used to stab things for pretty ok damage. Makes wrestling very interesting since each tentacle counts as a limb. Like all demons has [NO_EAT], [NO_DRINK], [NO_SLEEP].