Beth is one of the twin children born to Queen Lilia and Prince Itaka (King Astralta III) during an AI machine invasion. Separated for protection, Beth was entrusted into the care of the gladiator Balga by the nanny Tarama. She was subsequently raised by Il, a female cyborg ronin and refugee from Murat. For safety during her upbringing, Beth disguised herself as a boy.

Beth and her twin, Jimsa, possessed innate supernatural powers, including the ability to project individual energy beams. These abilities resulted from generations of selective breeding by a Murat refugee cabal, who engineered the Astrian royal bloodline to produce individuals capable of resisting the machines. The twins' powers were deemed essential for the planet's survival.

Reunited with Queen Lilia and Jimsa as teenagers, Beth was persuaded to combine her energy beam power with Jimsa's against the machines. Their combined beams produced a magnified effect, though this only temporarily impeded the invaders. In the final conflict, the High Priest Kufu and Il destroyed the machines by triggering a planetary explosion. Beth and Jimsa escaped to safety in a space capsule, drifting through space, their cells destined to seed life on a primitive planet through evolution over eons. The narrative implies the twins may reunite through reincarnation in the distant future.