|Although this article is based on canonical information, the actual name of this subject is conjectural.|
The Curse of Brotherhood of Seven removed the essence of the victim from his or her natural body and imprisoned the essence into an inanimate object. The victim would suffer from the curse and would not be able to return to his or her body until he or she has killed all seven demons of the brotherhood.
One of the seven demons performed this curse to a demon hunter Sid and trapped him inside a dummy. Sid suffered from the curse for several decades, during which time he tracked and killed all but one of the demons. By the spring of 1997, he managed to track the last demon of the brotherhood in Sunnydale, where a hellmouth is located. He used a student by the name of Morgan to help him get around the school. With the help of the slayer Buffy and the Scoobies, he was able to kill the demon, moments before it could successfully retrieve a brain to regenerate. However, as Sid's body has long since decomposed, Sid died once the curse was lifted.
In the non-canon video game Buffy the Vampire Slayer: Chaos Bleeds, the First Evil intervened after the curse was broken and trapped Sid's soul in a duplicate dummy body as he had pissed it off while human meaning that breaking the curse was for nothing. Sid aided the Scooby Gang defeat the First and once it was dispersed by Hope's Dagger, was finally set free as he should've been when the curse was broken.