Fire Monsters Against the Son of Hercules

Maciste contro i mostri English Translation Fire Monsters Against the Son of Hercules is a 1962 Italian film directed by Guido Malatesta that was filmed in Yugoslavia and Italy. In the American version Maciste is called Maxus.

Set in the Ice Age, a nomadic tribe of sun worshippers reach an area they decide to settle in. When Idar and Rhia, a young couple of the tribe come across a water monster, the monster is killed by Maciste with a spear. The two ask Maciste to join their tribe but Maciste explains he has a destiny to fulfill of righting wrongs and must leave.Soon afterwards a cave dwelling tribe of moon worshippers led by Fuwan attack the village and carry off the sun worshippers women. Maciste returns to the sun worshippers and enter the moon worshippers underground city through a river. There he discovers Moah, whose father and brother who had formerly led the tribe were murdered by Fuwan and wishes to take Moah. Moah explains that the moon worshippers will sacrifice the captured women in a celebration of the full moon that night. ........

Source: Wikipedia