In demonology, Shax (also spelled Chax, Shan, Shass, Shaz, and Scox) is a Great Marquis (and a Duke to some authors) of Hell, and has power over thirty legions of demons. He takes away the sight, hearing and understanding of any person under the conjurer's request, and steals money out of kings' houses, carrying it back in 1200 years. He also steals horses and everything the conjurer asks. Shax can also discover hidden things if they are not kept by evil spirits, and sometimes gives good familiars, but sometimes those familiars deceive the conjurer.

Shax is thought to be faithful and obedient, but is a great liar and will deceive the conjurer unless obliged to enter a magic triangle drawn on the floor. He will then speak marvellously and tell the truth.

He is depicted as a stork that speaks with a hoarse but subtle voice; his voice changes into a beautiful one once he entered the magic triangle.