Physis, a blind woman revered as a spiritual figure or 'goddess' by the Mu people, employs Tarot cards to foresee the future. She is not a natural Mu but a genetically engineered human, created without inherent psychic abilities as part of the same cloning program that produced Keith Anyan. The original Mu leader, Soldier Blue, granted her psionic powers, enabling her role as seer and advisor aboard the Mu mothership, where her visions provide crucial guidance. Unbeknownst to Keith Anyan, Physis is his biological mother. She and Blue share a profound mutual reliance, with Blue seeing her as a source of hope and stability.

After Blue's death and Jomy Marcus Shin's rise to leadership, Physis continues her supportive role, though her borrowed powers fade, diminishing her influence. During the human invasion of the Mu colony Naska, Keith Anyan captures her as a hostage; Jonah Matsuka later secures her rescue. Physis survives the final conflict on Terra and the destruction of the supercomputer Grandmother. The manga depicts her leading survivors during Terra's collapse, surrounded by escapees facing an uncertain fate. A distant epilogue across adaptations suggests her potential reincarnation, symbolized by children representing her and Blue returning to a revitalized Earth. The anime adaptation specifically frames her connection to Keith as an "Evil Twin" dynamic stemming from their shared genetic origins.