Queen Diona is the benevolent and noble ruler of an tribe of amphibous, blue-skinned Amazons who reside near the ruins of Mount Rushmore. Diona was driven from her kingdom by the wizard shark-woman, Striya, who seized her throne and planned to raise an army to conquer the surface world. Dionna and one of her soldiers were battling Striya's female Shark Troopers when they were saved by the arrivals of Thundarr, Ariel and Ookla. Diona explained Striya's intentions and the group agreed to help her regain her kingdom. Striya was eventually defeated and banished to parts unknown after a magical battle with Ariel and Diona was restored to the throne.