Walter Halloran’s Crucifix

Origin
Walter Halloran was a Catholic priest who participated of the demonic possession and exorcism of teenager Roland Doe. The tale would eventually inspire the novel and film “The Exorcist”.

Effects
While not only used in the story that inspired "The Exorcist", but somehow made it's way onto the set. This double dosage of exorcism infused it with the ability to drive the purest form of evil out of a person’s soul, but that soul will then cause mayhem until it finds a new host. This was the reason behind all of the incidents that happened on set of the movie, ending with it taking residence in Mercedes McCambridge's son, making him kill his wife, children, and himself.