The Devilkin, or Little Devil, is a spirit from "Frosting the Snowman", a short comic from The Real Ghostbusters Magazine Winter 1990. One devilkin possessed various snowmen, which then merged into a giant snowman. Winston devised a plan to have a snowball fight with it, so it would fight back using snowballs from its own body. Once weakened, the Ghostbusters trapped the devilkin.
A devilkin is supposed to be very clever and playful like a child.