The Harbinger Parasite, the size of a small thumb, attaches to a host's back with needle-like appendages that pierce the skin and inject mutagenic enzymes.

Over several days, the host painfully transforms, becoming taller with darkened, shifting skin. The head morphs into a grotesque mouth with sharp teeth, and long, barbed tentacles emerge from the back for climbing, grappling, and attacking.

The transformation enhances senses, reflexes, and strength, driven by the parasite's malevolent will.