Grim Reaper

The Grim Reaper is an undead entity that visited Billy Acachalla and Sally Acachalla. He resides in the Underworld.

Origin
The origin of this character is unknown.

Acachalla visit
After Hilly and Sally enter the kitchen, Grim is seen from a distance stalking them. He then approaches, asking why they're playing with paper towels. After Billy claims it is his "sacrifice" and freaks out, Grim tries to calm him down by saying he doesn't need one. He reveals that he came to claim their souls and to talk about that. He claims that the family broke the laws of nature by respawning instead of dying. He then tests the theory of Billy not being able to die and pulls out a special pistol that makes sure he stays dead. After conversing a bit, he opens fire, sending Billy flying backwards.

This doesn't work, and Billy comes back to life and noclips back to them. After killing him again, Grim becomes confused and spits out "What?!". After realizing that Sally owns the Underworld and is his boss, he still tries to kill them as he is curious, and suggests to kill them in a variety of ways.