Possession

Possession was the magical process of one thinking creature taking over another one's body.

Most spirits in the Prime Universe were capable of possession, and possessing sentient beings from a universe other than the Prime would allow themselves to “anchor” themselves to those universes, being able to linger there beyond Halloween. When the Great Ghost and his legion escaped the Spirit Realm on Halloween 2019, they possessed a great number of beings including the Gang of the Green Gorilla and some of Madame Tarsa's magical marionettes. The Great Ghost himself chose the Queen of the Black Market as a vessel, prompting her to remark rather casually: “My third possession in fifty years. I have got to invest in a couple of sturdy warding amulets”. (PROSE: The Ghosts and the Machine)