1 Villager: Well, I'm afraid I'm going to have to call the town guard to arrest you and have you tried for theft and excessive use of fire magic.
2 Kyros: What are the penalties for those?
3 Villager: Pretty severe, but not as harsh as what's written in our legal code for mind control.
3 Kyros: Oh?
4 Villager: Yes, possession is nine-tenths of the law.

Intriguingly, Wikipedia defines the mind-control sort of possession strictly as the controlling of a human body by some sort of spirit, god, demon, or other disincarnate entity, or by the Devil. Nowhere at all does it mention the possibility of being controlled by someone with a physical body. I suspect most people would broaden the definition to include that though.

---

2019-03-02 Rerun commentary: Wikipedia has changed a bit over the years. I was thinking that by now, ten years later, there might be some information about the possibility of being possessed by other people. But nope.

The spirit one does mention possession by aliens. Which I suppose is the opposite of this type of possession.