>>11347792
My own OC is a lich girl. Wrote some stuff with that in mind. Her getting overpowered by some holy order but since they couldn't find her phylactery, they decided to bind her in a sanctified blessed frame that would simultaneously continuously inflict a slight burning sensation on her skin and nullify her magic. She is moved deep underground to a prison housing several powerful immortal beings they managed to capture.

They are treated as guinea pigs to develop new tools and magic, like the prison idea mentioned earlier. Eventually they do find the lich's phylactery but instead of destroying it, they embed it into a collar which they lock around her neck.