Hercules in the Haunted World(1961)

Original title: Ercole al centro della terra

Upon his return from battle in the previous film, the great warrior Hercules learns that his lover, Daianara, has lost her senses. According to the oracle Medea, Dianara's only hope is the Stone of Forgetfulness which lies deep in the realm of Hades. Hercules, with two companions, Theseus and Telemachus, embarks on a dangerous quest for the stone, while he is unaware that Dianara's guardian, King Lico, is the one responsible for her condition and plots to have the girl for himself as his bride upon her revival.