171 DOPPLEGANGER RESEARCH FACILITY. This laboratory holds six vertical glass tubes, each three feet in diameter and reaching from the floor to the ceiling.
Five hold what appear to be gray skinned corpses of men and women floating in a bubbly transparent liquid. Each is horribly deformed. For example one has no lower jaw and has dozens of toes and fingers on each extremity. Another is hunchbacked with flat skin instead of eyes and a mouth. These are actually the bodies of dopplegangers that have been stimulated by researchers to attempt to learn how they change shape.
The last tube holds an unconscious living doppleganger in its true form.
Doppleganger (AC 5; MV 9”; HD 4; hp 19; #AT 1; D 1-12 or By weapon type; SA Surprise on 1-4, Mutable form; ESP; SD Immune to sleep and charm, save as F10; XP 406)
If it is set free, it will serve its rescuers faithfully with genuine and sincere devotion for 1d4+2 weeks. At that point it will use its abilities to flee into the dungeons of Castle Triskelion. It will, however, retain its fondness for the adventurers who rescued it. The Dungeon Master should assign a chance that it will dramatically show up to help the adventuers when they are facing unusual difficulty in an encounter in the dungeon.