One of two emissaries sent to Earth's surface in 1932 by an advanced subterranean civilization, Avatar arrived alongside her sister Annette, bringing two powerful energy sources intended as a test for humanity. These resources were seized by opposing factions during World War II, leading Avatar to align with American forces.

She commands the technologically advanced submarine-battleship Liberty, armed with three bow-mounted drills and formidable weaponry including wave-motion guns and gravity-based attacks. Awakening from a decades-long coma in the present, Avatar concludes humanity has failed her civilization's character test due to its propensity for conflict. She launches a campaign to exterminate surface life by deploying massive microwave-emitting cylinders into orbit, forming a ring designed to irradiate the planet.

Her methods rely on manipulation and deception, such as luring a U.N. fleet to the secret base housing the reconstructed battleship Ra to provoke a fight. She shares a Cain and Abel dynamic with Annette, growing estranged during their time on the surface. This rivalry escalates into direct confrontations where Avatar attempts to eliminate Annette and her allies.

Avatar meets her end during a climactic battle against the Ra. Despite deploying the Liberty's full arsenal, including drill missiles, her attacks are countered by the Ra's rocket-propelled anchors. The Ra executes a ramming maneuver, plowing through the Liberty's bow and destroying the vessel, resulting in Avatar's death before her plan reaches completion.