Demon

"Go back to the Nether and tell your master I'm coming for him next!"~Steve threatening a Demon

Demons are effectively the most popular enemies in the Death will Come mod. They spawn in the nether and they shoot fireballs, as well as setting the player on fire when they touch them. They can also use an attack similar to the Flamethrower's fire. They have a one percent chance to drop a Flamethrower. Their Halloween Costume is the Infernal Imp.

Grim Reaper's Encyclopedia Entry
Did one of your mines happen to go so deep that you discovered a Perdition pit of Hellfire? DID ONE, STEVEN?!?!

Trivia
Interestingly enough, "Perdition" is not a made up word. It is a synonym for Hell.

The "D" in the label for the forums for this mod appears to represent the demon as it has two grey horns, two yellow angry eyes, and is colored red.