From The Mega Man Universe
Atlas is a soldier who survived the destruction of her country by Mavericks. Prior to the events of Mega Man ZX Advent, she was selected to be a participant in the Game of Destiny and given Model F. She believes that she can become a leader through fighting, and is a fierce adept of the philosophy of "survival of the fittest." Because of this, she is constantly stirring up trouble.
She debuts in Mega Man ZX Advent, making her first appearance in the Arctic Ice Floe accompanied by Thetis. She was interested in seeing the new Mega Man Model A after being told about it by Prometheus. However, she is disappointed by what she sees, calling the new Chosen One a "kid" who "became a Mega Man by accident" and retreats, leaving either Grey or Ashe (depending on who the player has chosen) at the mercy of a Pseudoroid.
Atlas is later found in the Oil Fields attacking the Raiders' airship which crash landed as a result of the Maverick attack from the beginning of the game. Intending to turn every single Raider present into nourishment for Model W, she is stopped by Grey/Ashe. Despite her defeat, Atlas manages to escape and isn't seen again until the rise of Ouroboros, when she corners the protagonist with the aid of Aeolus, Thetis and Siarnaq, intending to destroy the Mega Man Model A despite the fact that the four were used by Master Albert from the beginning. However, the four are stopped by either Vent or Aile (determined by whether the protagonist is Ashe or Grey respectively), who demands the four to return their Biometals while Grey/Ashe goes after Albert. However, fighting four Mega Man at once proves difficult for the Mega Man Model ZX, and when Ouroboros begins to collapse after Albert's defeat, Model Z prompts himself to stop the four while the Model X Chosen One rescues Grey/Ashe. Although Model Z appears to be against overwhelming odds, Atlas is shocked to find herself seemingly paralyzed by her own Biometal along with the others as Model Z claims to know the four Biometals better than their users, mere moments before Ouroboros explodes in the sky.
It is later revealed in the Expert Mode ending of the game that Atlas not only survived the explosion along with Aeolus, Thetis and Siarnaq, but also that she is still in possession of Model F and that she is now sided with Master Thomas in the latter's quest to reset the world.