Demons are residents of Hell. They were introduced in the Broforce full release and only appears during the Hell Campaign. Some, such as the Undead Mook, Engorged Mook, Hellhound, Skull Turret and Executioner are mostly enhanced versions of their regular counterparts, others are new enemies.
Undead Mook - Trigger happy zombie, satisfied now?
Engorged Mook - Guided bombs that can jump, sounds like balls.
Warlock - Magically generates those guided bombs around you while having their high-up life, useless without magic.
Skull Turret - Decreased fire rate with enhanced armament, is it worth it?
Hellhound - Once eaten something it won't get stronger but replicates by five, mass infantry.
Skinless Mook - Leeches who does nothing other than slowing you down, throw them off!
Lost Soul - Scary homing skull, out for your blood.
Boomer - Complete with acid faucet and explosively replicates some small bombs when they fall, no wonder it's name.
Soul Catcher - A little like the Boomer but when you got spotted by them they will instantly suicide and gift you with five homing souls, everything you don't need.
Bone Wurm - Bullhead on a wormy skeleton of spiral cord and sends scorching rain complete with homing souls, a brutal savage waiting for extermination.
Executioner - He doesn't use an axe but that doesn't matter, out of the frying pan?
Satan - The demon who's responsible for all of the above and some of your previous troubles, finish him once and for all!