Our resident agony aunt has been busily answering questions – but because our third issue of Shards: Worldbuilding Zine has only 44 pages, one of them’s had to be dropped.
So instead of completely removing it, I’ve decided to post it here for all to enjoy:
Dear Letter Lich,
I’m compelled by my god to kill a demon, but he’s in my friend’s body – HELP!
— Liam W.
You should arrange for your friend to become undead. Once they’re dead the demon will likely be forced out (most demons can only possess either the living or the dead, not both) and you can safely slay it, while you await your friend’s resurrection.
If you have the skills, lichdom is an excellent choice, but the varieties are endless. Vampires are said to retain their minds, but I find they tend to be impulsive; then again, so are mortals much of the time.
The death and resurrection approach is actually viable even if you’re not willing to bring your friend into undeath – you are doing your god’s work, asking them to safeguard your friends soul and return it when the demon is slain is a plausible option.
More likely you’ll want to seek out a rite of exorcism, or similar – something that can drive the demon from the body. If that is impossible, or unavailable, the backup plan is generally torture – capture the demon, and inflict agonies upon it (and unfortunately your friend) until it voluntarily leaves their body to face you. -Ed