Goliath and the Dragon

La vendetta di Ercole literally Revenge of Hercules, better known as Goliath and the Dragon, is a 1960 ItalianFrench international coproduction widescreen peplum film starring weight lifter and gymnast Mark Forest in his debut film role and Broderick Crawford as the villain. The identity of the title character was changed from Hercules to Emilius known as Goliath for release in North America by American International Pictures to tie in with their previous use of Goliath in Goliath and the Barbarians 1959. The film features special make up by Carlo Rambaldi.

The film begins with HerculesGoliathEmilius entering the underworld and defeating several monsters including Cerberus to retrieve the Blood Diamond of the Goddess of Vengeance. It is later revealed that King Eurystheus has sent HerculesGoliath on this task to ensure his death to gain allies who after Hercules death will join the King in an attack on Thebes. The episode is loosely based on the twelfth of the Labours of Hercules.Hercules returns to his wife Deianira to find that his teenaged son his brother in the American version Hyllus is in love with Thea the daughter of a King that Hercules believes murdered his family. The enraged Hercules refuses to let Hyllus have anything to do with Thea. The scheming Eurystheus has convinced Hyllus that Thea is really in love with Hercules rather than him and concocts a plan where a jealous Hyllus will murder his own brother. A slave girl Alcinoe gies Hyllus a poison to give to Hercules that she says is merely a potion to have Hercules fall out of love with Thea. Eurystheus himself wishes to marry Thea and install her as his Queen. ........

Source: Wikipedia