[Ah, now he has some vague idea of who called him. Very vague. He's basically forgotten him even as he was in the middle of his working. But he doesn't have any reason not to explain, and he likes talking about magic.]

It was not a curse, that is a different magic. It was a spell of... empathy. Demons cannot feel as humans can, but they gain their shape through their possession. Such an event leaves an opening in the soul, even if the demon is banished, through such ties, a demon can be granted some of the... gifts of humanity. For a short time.