Grim Reapuff

The Grim Reapuff is a hairless, fleshless puffle who wears a black hood and carries a scythe. He is responsible for the death of all puffles, for if they didn't die they would become zombies.

History
Unknown to most, puffles are not terrestrial creatures, but really are an amalgamation of microscopic extremophile aliens, minerals, and certain earth organisms. Their biology is completely different from most other organisms; they can live forever. Their brains are almost ageless and are able to repair themselves, but their bodies weaken throughout the years. Evantually, it'll hit it's weakest link, and the puffle will find it very painful to move (some puffle organs might be torn). However, the body doesn't stop functioning, it just functions very poorly. If the puffle endures this for a long time, it's brain will release certain chemicals, which will turn it into a mindless creature.