An Electromagnetic Being (電波生命体 Denpa Seimeitai, lit. "Radio Wave Life Form"), or EM Being for short, is a sentient being composed completely of electromagnetic waves. These beings play a key role throughout the Mega Man Star Force series. Most EM Beings can perform an EM Wave Change with a compatible human or other such entity, though others may fight on their own. EM Beings also have a pulsing body from energy (such as Omega-Xis' green pulsing body), but EM Wave Changes humans do not retain such pulse (besides Mega Man's arm in the first two games, although it is Omega-Xis' pulse).
Types of EM Beings
Planet AM is home to the AM lifeforms, or AM-ians. They are extraterrestrial EM Beings whose planet neighbored that of the FM-ians, but was destroyed by the FM King's weapon, Andromeda. Despite this, some AM beings survived as refugees on other planets, such as Omega-Xis.
In the Mega Man Star Force anime, the three Satellite Admins, who are also AM-ians, remind Omega-Xis that he is one of their kind, proof of which resides in his ability to convert humans into EM Beings.
Planet FM is home to the FM life forms, or FM-ians, and was the neighbor of Planet AM before it was destroyed by Andromeda. The FM-ians are also a race of extraterrestrial EM Beings who have EM bodies, and usually bear the names of constellations. They feed on negative human emotions and are the main villains in the first Mega Man Star Force game, although not all of them are evil.
The FM-ians' King, Cepheus, first believes that the BrotherBand transmission from Kelvin Stelar's satellite is a sign of hostility, and sends the EM Beings to Earth to destroy it with the Andromeda. However, Cepheus later decides to stop his actions when he realizes what the BrotherBand is, and begins work with the three Satellite Admins rebuilding Planet AM.
Mu EM Beings
In contrast to the AM and FM Beings, Mu EM Beings are native to Earth, and were made by the ancient culture of the Mu. The most powerful of these was Le Mu, who was made to be an omnipotent god of EM Beings to the Mu. Most Mu EM Beings are named after cryptids such as Phantom, Yeti, Plesio, and Condor. During the second game, Le Mu was known to have the ability to make copies of those four EM Beings, and it was shown that many more of them remained in a state of suspension within the continent of Mu. In an alternate future, the scientist Dr. Vega succeeds in awakening Le Mu, but fails at her goal of creating a Neo Mu Empire. Le Mu bears an offspring, Apollo Flame, who then wipes the Earth clean of humans and converts the existing EM Beings of the planet into his servants.
Only one other being is known to have been created after the genocide of humanity: the appointed leader of Apollo Flame's army, General Auriga. Whether he is a Mu EM Being or not is unknown.There are also lesser Mu EM Beings made by the Mu called Murians. These Mu can play the role of both soldiers and bodies for which the higher EM Beings fuse with to reach their EM Wave Changed state.
Artificial EM Beings
In Mega Man Star Force 3, humans have created their own EM Beings in the hopes of being able to synthesize EM Wave Changes and benefit from their use. These EM Beings are dubbed Wizards, as they operate the Hunter-VG in the same manner that their NetNavi predecessors operated PETs. Wizards may also materialize into the real world, if their owner allows them to.
The creation of Wizards has also caused a phenomenon called Noise to surface, and the Wizards themselves can be corrupted by it. There are also Noise Cards that the criminal organization Dealer use to deliberately corrupt Wizards and other EM Beings.
Extraterrestial EM Beings
The only known naturally occurring EM Being, neither AM- nor FM-ian, is the EM Being named Sirius from Mega Man Star Force 3. He is a powerful EM Being who both controls and resides in the Black Hole Server at the center of the Milky Way. Sirius searches the galaxy, drawing near planets and beings that he wishes to consume with the black hole and "collecting" them for his personal use and amusement. Among these are the data of defeated EM Beings as well as planets, such as the reconstructed Planet AM.
A predominant ability of his is to use the black hole to consume planets or other celestial bodies, and then convert desired parts of his "collection" into servants for his army, much like Apollo Flame. It is never said whether this ability is natural to EM Beings born of black holes, or simply one unique to Sirius.