The origins of Ra Moon are unknown, but it first came to Earth over 20,000 years before the 20XX period. According to him, he is responsible for instilling humanity's capacity for violence towards itself and developed technology which would allow the human race to destroy itself. Ra Moon intended to rule the Earth himself by creating an army of machines to serve him, but grew weary of humanity's pace of development and fell into slumber to wait for the right time when humanity had advanced to a suitable level of technology.
In the 20XX period, Dr. Wily was investigating an unusual electromagnetic phenomenon in the Lanfront Ruins and discovered Ra Moon. At this moment, Ra Moon awoke and analyzed the computers Wily had brought with him and used its own power to recreate 16 of the doctor's Robot Masters. He also assisted Wily in creating an entirely new robot called Ra Thor.
Ra Moon had initiated its plan to destroy humanity by emitting electromagnetic waves that disabled the majority of Earth's machines, including all of its advanced robotics. However, Dr. Light was able to protect Mega Man and a few other Robot Masters with a special coating that made them temporarily immune to Ra Moon's EM wave. With the planet plunged into a blackout, Mega Man sought out the source of the signal and found Dr. Wily and Ra Moon at the Lanfront Ruins. Mega Man battles his way through all of Dr. Wily's forces and also destroys Ra Thor before confronting Ra Moon's most deadly creation, the Ra Devil. Ra Devil proved to be immune to Mega Man's attacks, but Ra Moon was left vulnerable due to diverting all of its energy to Ra Devil. Using a double Mega Buster blast, Mega Man managed to destroy Ra Moon and collapsed the temple. With Ra Moon destroyed, the EM field covering the Earth was lifted.
Ra Moon is capable of generating energy fields that can disrupt electronics and disable advanced machinery as well as affect the minds of humans. The field he generates also has a toxic effect on human bodies and if he had continued it would have killed off the human race.
Ra Moon is also capable of creating robots in the blink of an eye. By analyzing pre-existing data, it can create a perfect copy of any robot design instantly.