Who's Who in the Spirit World is a spirit guide that was used to conduct research on the Ghostmaster.
The Real Ghostbusters
"Who's Who in the Spirit World" has an entry on the Ghostmaster and states the Ghostmaster is a Class 11. Ray Stantz checked a copy out from the New York City Public Library when he and the other Ghostbusters were battling the Ghostmaster. He revealed the troubling information to Egon Spengler after showing him the book.
Egon knew Saul Pendleton's name sounded familiar. He found an entry in Who's Who in the Spirit World about the Pendleton line. It stated the Pendletons were a line of necromancers who used ghosts to predict future events.
- Ray Stantz (2009).The Real Ghostbusters- "Revenge of the Ghostmaster" (1989) (DVD ts. 09:36-09:39). Time Life Entertainment.
- Egon Spengler (2019). IDW Comics- "Ghostbusters 35th Anniversary: The Real Ghostbusters" (2019) (Comic p.14). Egon Spengler says: "According to "Who's Who in the Spirit World," Pendleton comes from a long line of Necromancers, sorcerers who use ghosts to predict future events."