Is Poul and Karen Anderson's Dahut possessed? Surely some of her behaviour suggests this? See here and here.
I ask about possessions because I am currently reading about one in Miracle Monday. In the Inferno, Dante meets the soul of a guy who is still alive on Earth. The explanation is demonic possession. We have referred to a possession in CS Lewis' Perelandra and to another in Garth Ennis'
In real life, some people either are possessed or imagine that they are with comparable results.