Pandora was built along with her brother Prometheus by Master Albert.
Mega Man ZX Advent
She first confronts Grey, her younger 'brother', in the forgotten laboratory and attempts to kill him, referring him to as a defective. she later confronts him on the train level with Prometheus (this is the fist confrontation she has with Ashe), whereby the main character megamerges to form Mega Man A. She then decides that he may be of use and lets him/her compete in the "Game of Kings".
It is also later revealed that Pandora is permanently megamerged with a piece of Model W, allowing her access to mage-like powers.