Vestarnu commanded the Darius Empire's western forces as the West General, leading the specialized Iron Beasts unit. Her formidable and disciplined leadership earned her the designation "Iron Lady." She consistently maintained the stoic, composed demeanor befitting her role as a "Lady of War" within the military hierarchy.

Lee Jenshin, a crew member of the opposing Daiku Maryu, intervened to rescue Vestarnu during an assault by droid soldiers at Proist's secret quarry. This rescue resulted in Vestarnu suffering temporary blindness due to gunpowder exposure. Witnessing Proist's increasingly dishonorable and ruthless tactics firsthand during this event precipitated her growing disillusionment with the Darius leadership and directly led to her defection from the Empire.

Following her defection, Vestarnu decisively shifted allegiance from antagonist to trusted ally. She assumed command of the Daichi Maryū, one of the Three Dragon Ships originally aligned with Darius. In this new role, she became the primary pilot of the powerful mecha Vulking after its capture from Proist, placing her in direct opposition to her former comrades.

Her journey traces a complete transformation from a loyal, high-ranking military commander within the antagonistic forces to a captain and ally fighting alongside the protagonists against her former empire.