The 44th spirit of the Goetia. He is a great Marquis and appears as a stock dove and speaks with a hoarse, subtle voice. His office is to take away the sight, hearing and understanding of any man or woman at the command of the summoner. He can also steal money out of kings' houses and carry it again in 1200 years and can also fetch horses or many things at the command of the summoner. He must be forced into a triangle first or he will deceive the summoner and tell many lies. He can discover all things that are hidden and not kept by wicked spirits and sometimes bestows good familiars. He commands 30 legions of spirits.
"One of the 72 demons of the Goetia. He is the great marquis of hell and controls 30 legions of demons. He appears as a stork with a raspy voice and is a liar, but will speak the truth when in a magic triangle. He can take away the use of people's eyes, ears or mouth, and is adept at finding hidden treasure, likely because he is fond of stealing treasure to take back to Hell."
Shax appears during the Challenge Quest "Help the People of Ikebukuro." He has taken to driving the humans living in the underground district of Ikebukuro insane, forcing them to violently fight over supplies to present to Shax. When the party finds him in front of the ticket gates of Ikebukuro, he is enjoying the spectacle that he has created while taunting Ken about the state of the town. Defeating Shax returns the people of the district to normal.
Shax can teach Nanashi the Bufudyne, Mazandyne, Makajamaon and Will of Wind skills through his Demon Whisper. He benefits from learning Force, Ice, ailment and support skills.