Hercules In The Haunted World (1961)

aka: Ercole Al Centro Della Terra

Hercules (Reg Park) must journey to Hades itself to retrieve the magic stone that will free his love from the powers of darkness. Upon his return from battle in the previous film, the great warrior Hercules learns that his lover, Daianara, has lost her senses. Acording of 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, unaware that Dianara's guardian, King Lico (Christopher Lee), is the one responsible for her condition and plots to have the girl for himself as his bride upon her revival.