Vestaanu held the rank of West General in the Darius Empire, commanding the formidable Iron Beasts. Initially embodying stern discipline and unwavering imperial loyalty, this earned her the moniker "Iron Lady." She spearheaded the deployment of Darius's mechanical monsters against the Daiku-Maryu crew during their campaign to halt the empire's invasion.

Her loyalty shattered when she discovered the morally corrupt and dishonorable tactics used by Proist, the East General leading the Darius war effort. This revelation directly violated Vestaanu's principles, triggering her defection. She subsequently allied with the Daiku-Maryu resistance, taking command of the Daichi Maryū, one of the Three Dragon Ships previously aligned with Darius, transitioning from antagonist to ally.

In combat, Vestaanu piloted the powerful mecha Vulking, renowned for its ferocious defensive systems and long-range weaponry, including signature attacks like the "Hydroroot Cannon" and "Endless Burn." Her exceptional piloting skills made her a valuable asset both for the Darius military and later the resistance.

Interpersonal dynamics fueled her development. Proist's manipulation, including brainwashing tactics enforcing loyalty among generals, deepened Vestaanu's disillusionment. Her eventual collaboration with Daiku-Maryu pilot Lee Jenshin proved instrumental during the operation to seize the Tenku-Maryū and break Proist's control over other brainwashed individuals.

Vestaanu's arc culminated within an alliance of former Darius generals opposing Proist's escalating threat. This late-series coalition united Vestaanu and the reformed North General Nouza against Proist's destructive ambitions.