Jeffrey Dahmer was a Satanist who practiced Astral Projection

...we know this since he was asking favors of beings:

The story of Dahmer's arrest and the inventory in his apartment quickly gained notoriety: several corpses were stored in acid-filled vats, and implements for the construction of an altar of candles and human skulls were found in his closet. Accusations soon surfaced that Dahmer had practiced necrophilia and cannibalism. Seven skulls were found in the apartment.
[link to murderpedia.org]


Dahmer also planned to build a "temple" out of 10 of his victims' skulls and two skeletons, which he believed would give him special powers to improve his financial and social position, Becker said. Dahmer also drew plans for the temple's altar.
[link to community.seattletimes.nwsource.com]


Drawing of the alter
[link to theloosecannonbuchanan.tumblr.com]
[link to fineartamerica.com]