Prometheus

Prometheus (プロメテ, Puromete) is a mysterious character from Mega Man ZX and Rockman ZX Advent. He and his sister Pandora are servants of Model W. He wields a beam scythe and uses fire-based attacks in battle.

Personality
Prometheus is a very arrogant fighter who enjoys nothing more senseless killing and a good battle. He also seems to hold a grudge against Vent/Aile and refers to him/her as a pawn in his game. His personality has yet be further explored, as his connection to Ashe.

Mega Man ZX
So time prior to the game's actual events, after Serpent had excarved the Biometals Model H, Model F, Model and Model P, Prometheus and Pandora approached Serpent and after their meeting, several company workers mentioned that both Serpent and Slither, Inc. had changed their way of business.

Prometheus, along with Pandora, worked for Serpent in order to reawaken the dormant Model W. Prometheus encountered Vent/Aile in one of the stages and retreat upon defeat and latered appeared again, this time teaming up with Pandora to fight the player. After both of them were defeated, they disappeared again and weren't seen again, not even to assist Serpent in his battle with Vent/Aile, apparently because he had already fullfilled his role in the game of Model W.

Mega Man ZX Advent
It's revealed in ZX Advent that both Prometheus and Pandora are sibling Reploids and Model W fragments created by Master Albert as Mega Men to help the Game of Destiny along. They were both intentionally created with a short life span by Albert so he would constantly have them under his thumb. Prometheus kills who he assumes is Albert at the Submerged Volcano Area, when in reality, it was merely Albert's body double and then proceeds to fight Grey/Ashe alongside Pandora. After the fight, Prometheus and Pandora are killed by Model W absorbing energy from them. Their bodies were left in the Submerged Volcano Area.

Trivia

 * In Greek mythology, Prometheus was the Titan who created man from clay in the image of the gods and later gave man fire to survive. Prometheus was punished for this by being shackled to a mountain peak and having an eagle pick at his liver for eternity. Man was punished by receiving Pandora and her opening her jar/box.