Tergol
The child-thief. He is named in the very opening of the book: "Our young ones are taken by the child-thief Tergol, known for his vile crimes and alchemy of flesh." He operates near the Valley of the Unfortunate Undead — the same passage that introduces him also introduces the Valley.
The Bedeviled Dungeons table includes among its possible occupants: "Tergol's escaped experiment."
Connections
Gaps / Expansion Notes
Tergol has no stat block, no lair, and no description beyond "vile crimes and alchemy of flesh." His escaped experiment is a generic encounter line. He is one of canon's most evocative blank slates — a named, hated villain everyone knows about, awaiting a writer.