Taiyou no ouji Horusu no daibouken (1968)

Horus, a kid living in an unnamed Scandinavian/Eastern Europe culture of the Iron Age, recovers the Sword of the Sun from the rock giant Moog and learns from his dying father that he must returns to his ancestral territory. In the process, he defends a village from the attacks of Grundewald, a warlord/ice demon and befriends the enigmatic Hilda, a lonely and beautiful girl who sings haunting songs (and who hides a terrible secret).