So demons would be a type of fiend that deal and resist both shadow and elemental damage, but still weak to piercing damage. Because of this mix of damage types for the monster, it would probably be used in some sort of fiend-themed danger mission or expansion mission.

Appearance
Perhaps they would look similar to devilites, but have horns, red eyes, unused large wings, and have more defined features with larger bodies. Demon lords would be even larger and have twisted, black horns, purple eyes, and float slightly off the ground with their wings. They also have spiked tails. The names of the differently themed demons could be Haters for Fire, Isolators for Freeze, Agitators for Shock, Damners for Curse (a bit iffy on this one, I know), and Toxicants for Poison. Ideas for better names are most welcome.

Attacks/Abilities
As a standard attack, the small demons take a little time to conjure up an energy ball, like the ones that gun puppies shoot at you, but much bigger, like the ones those armored, stationary constructs spin around themselves, and they launch the thing at you, dealing shadow and elemental damage, with a possible status effect. An alternate attack would be to charge up the ball for a little longer before they smack the ground in front of them, causing a brandish-like wave of bursts to shoot in front of them. Demon lords cannot shoot the normal energy ball, but can teleport, similar to wolvers, and whack you back to Haven with a spiked mace, or perhaps something easier to model. Demon lords have more health than their minions, whom they can heal with a brief aura, like the gremlin menders, which also boosts their attack power, like wolver Alphas. Ooh, scary. Small demons could only become demon lords if a lord dies, and demon lords do not become small demons if all small demons are defeated. Oh, and upon death, they spawn some explosive gel.