What is a group of demons called?

Answer 1

Monsters come in "gaggles" unless they already fit an existing grouping:

• 3-eyed rabid cows come in herds;
• Birds come in flocks or Hitchcocks;
• Werewolves come in packs;
• Cigarettes come in packs, too;
• Vampires come in through open windows;

Answer 2

Generally, they are called "legions".

Answer 3

legion