On the way back to Tavia, the party encountered Father Gareth and Suchet who lead them to a sunken road where demons ambushed them. Fighting off the demons, the party realized that Father Gareth and Suchet were doppleganger demons – Ankou demons (see below). Fearing to harm their friends, they intimidated the captured demons into revealing where Suchet and Gareth were (rather than killing the demons outright), and rescued their friends.
Suchet and Gareth are very ill (in game terms drained of strength) but will recover with some restoration magic. The two were hidden in a crypt, guarded by a ghoul of exceptional power.
After looting the ghoul’s crypt, they took their friends to the nearby village of Tomalin, where the party has rested and recovered all HP and spells. Note: Suchet and Gareth are still drained of strength.
An ankou demon is sort of like a doppleganger in the sense that it can pass as someone else. In this case, the substitution is extremely strong, thanks to a bond that remains to its living victim.
The demon can change its form, much like the fairly common alter self spell of wizards and sorcerers. However, it has a much stronger form of mimicry: it can beguile a victim, rendering the victim catatonic. Then, after close physical contact for some hours, it can take a form of the victim that is impenetrable to most forms of magic, such as a paladin’s ability to discern evil.
Only the most potent of vision spells can reveal the ankou demon for what it is. Anything else will only reveal what would be revealed if the spell were cast on the victim because somehow the ankou channels such magics to the victim, who remains in an unconscious state.
As long as the victim lives, the ankou can also speak and read any languages of the victim and has access to much of its memories, although not special powers like spells.
The linkage is not beneficial to the victim. Rather, the victim wastes away, slowly if the ankou cares for the victim with food and water, quickly if not. Ankou do frequently tend to their victims to further their disguise, not out of good nature, of course, but even in the best cases a victim rarely lives more than a few weeks in this state.
Slaying an ankou demon while linked to its victim kills the victim and the demon. To save the victim, the victim must be physically found and then the magic link severed through some sort of magic circle, or the like. Even then, the victim is usually quite weak, requiring the restoration magic of a powerful priest to fully recover.
In its natural form, ankou demons appear as a slender, tall, genderless humanoid with tentacles around its mouth, coal black eyes, few features and dark gray to black skin.