Gigano Dragon embodies the form of a Chinese dragon, setting him apart within his narrative. His origins lie with King Agingo, ruler of Planet Eden's Overlanders, who declared his race supreme. Agingo initiated conflict by enslaving other beings and desecrating sacred sites, sparking a war against Prince Davun-Fel that concluded with the Overlanders' banishment to an undead planet.

Agonized by defeat, Agingo's intense hatred unintentionally freed Diamond Ryugu from imprisonment. She drained the life force of their world, Mugen, using her Void power to transform Agingo into Gigano Dragon and his people into Dragozaurs. They subsequently worshipped Ryugu as their goddess. Serving as her second-in-command, Gigano remained indifferent to Ryugu's mission of harvesting planetary life forces, consumed solely by his desire for vengeance against his ancient rival Tyranno.

This singular focus defined Gigano's actions. He once attacked Tyranno's human ally, Kaito, provoking Tyranno to hurl him over a cliff in decisive defeat. Their rivalry culminated in a final battle where Tyranno destroyed Gigano, though Gigano offered a cryptic farewell before perishing. His spirit endured, stored within a crimson crystal by Malefor and later bound to Kin Einmortal's Thule Medallion. Kin discarded the soul, leading to Gigano's resurrection.

Resurrected, Gigano's vendetta expanded beyond Tyranno to target the descendants of Prince Davun-Fel—specifically the human successors known as the Bistrorangers. In later confrontations, he demonstrated near-total immunity to conventional attacks and strategic countermeasures.

The character also featured in the supplemental OVA "Gigano Dragon Strikes Back!!", included with his toy release.