Altered Beast is a side scrolling beat 'em up game with light platform elements. It has five levels and can be played by up to two players simultaneously. Combat takes place across five levels set in Ancient Greece and populated by aggressive undead creatures and monsters resembling those from Greek mythology. The demonic god Neff, known as Majin (魔神, "magician", "sorcerer", "demon god", ...) in Japan, waits at the end of each level. Players can punch, kick and jump.