Based on Richard Wagner's opera of the same name, although extremely loosely. Alberich, the last male descendant of the Nibelung 'clan', steals a singularly powerful nugget of gold from the planet Rhein. He tricks young Tadashi Daiba into forging a ring from it that will enable him to conquer Wotan, the ruler of the planet Valhalla, and become all-powerful in the universe. Aberich's sister Meeme opposes his ambitions and seeks the aid of Captain Harlock, Tochiro, Yattran, and Emeraldas: an alliance no villain can withstand. The adventure ends with Daiba and Harlock preparing to unmake the Ring and return the gold to the planet Rhein.

Related series are;
Cosmo Warrior Zero
Harlock Saga
Maetel Legend
Queen Emeraldas
Space Pirate Captain Herlock
Arcadia of My Youth