Aleister Crowley was an English occultist responsible for the founding of the religious cult of Thelema. He saw himself as the prophet who was responsible for informing humanity that they were entering the new Aeon of Horus. He also claimed to have great proficiency at summoning the demons of the Ars Goetia, even going so far as to claim that he had been able to summon Choronzon but had been unable to control it.
Shin Megami Tensei II
Crowley appears as the human leader of Netzach, a realm in the Expanse. After rambling about how Lucifer won't let him have a Sabbath, he turns into Master Therion and takes his anger out on Aleph. He is eventually killed by Aleph.
Devil Summoner 2: Raidou Kuzunoha vs. King Abaddon
Although he doesn't make a physical appearance, Crowley is the client of two Case Files in the game. The first is Wise Demon Required, being a request for a Thoth. The second is I Can't Contain It, where he asks for an amulet to protect himself from demons and have dream of Sabbaths be made a reality.