Zelene Birkenbaum (ゼレーネ・ビルケンバウム, Zerēne Birukenbaumu?) was a soldier and researcher from the Giadian Empire. She developed the Legion in the hopes of removing humans from the battlefield. She was assimilated into the Legion as a Shepherd with the callsign of Mistress.
The Merciless Queen is an Ameise with lunar-white armor and a golden optical sensor unique to the unit. The Ameise bore the Personal Mark of a goddess leaning against a crescent moon.
Zelene was acquainted with Shin's father—Reisha Nouzen—as fellow researchers.
Zelene used the Mariana Model AI developed by Viktor Idinarohk in tandem with the Alliance's superior Feldreẞ technology in order to create the Legion. She began developing the Legion when her older brother lost his life; a friendly aircraft accidently shot him down. She became reclusive after the event, Vika himself stated that she was a witch which cursed the world. Zelene's personal beliefs and experiences would shape how the Legion would operate. An example would be that the Legion could not develop its own weaponized aerial units, as she had a vehement hatred for aerial combat following her brother's death.
Zelene was fully committed to making the Legion a reality, her fury only strengthened by her limited lifespan. She would apparently pass away from disease shortly before the first series of Ameise was produced. Neither her body or death certificate was ever found, due to assimilating with the Legion herself as the Merciless Queen.