Duke Oasis is a heroic character fighting Earth's invaders from Planet Muzanda led by King Bull in the OVA "Ippatsu Hicchū!! Devander". He stands alongside the protagonist, Kazuma Harukaze, who transforms into the masked hero Devander. Duke Oasis utilizes advanced technology, including the mecha steed Robony, as part of the group defending Earth. His actions contribute to the central conflict against the invaders' UFO siphoning "Gaia Energy" above Mt. Fuji. Duke Oasis's background, personal history, character development, expanded role beyond the main heroic ensemble, origins, relationships, narrative evolution, and presence in spin-offs, additional media, or expanded universe content remain undisclosed.