Eldritch Earth: Five Hacks Deep

A Hell Stalker is a large, gangly-looking humanoid, from 7 to 10 feet tall, created by dark magic from the blood of human sacrifices. The Stalker is given a target on its creation which it hunts and tracks until it or its victim is dead. If a Hell Stalker kills its target, it will rip off his head and take it to a dark cave to plant it, where it will grow into another Hell Stalker, joining its creator in hunting innocent victims and tearing off their heads.