Evil Energy

Evil Energy (悪のエネルギー) or Evil Alien Energy is a mysterious sentient energy source of alien origin (hence its name) that appeared in Mega Man 8. Usually, it looks like a swirling purple flame in the shape of a skull. According to Duo, the Evil Alien Energy absorbs evil within a person's mind and then multiplies to infect others--mainly robots, in the case of the game. Due to this method of replication, the original source can only be harnessed by beings of pure evil. Duo hunts down this Evil Alien Energy to stop it from infecting the whole universe and possesses the ability to heal its victims if their minds are not completely consumed by evil.

Story
In the opening of Mega Man 8, Duo is seen in space, battling an evil-looking robot utterly consumed by the Evil Alien Energy (it is unknown if this is another victim of the Evil Alien Energy or an actual manifestation of the energy itself). He manages to defeat the robot, but both combatants fall to Earth, impacting a remote island. Unfortunately, the island happens to be Dr. Wily's secret base, allowing the mad scientist to discover the remaining Evil Alien Energy. He escapes with his prize as Mega Man shows up, and eventually learns how to harness its special powers and its properties.

Using the Evil Alien Energy apparently allowed Wily to power up his robots and construct a massive new fortress in the heart of a volcano. His first four Robot Masters carried capsules of Evil Alien Energy in their bodies, although it isn't known if it had either augmented their powers, manifest a bad personality, or was simply a power source.

When the first capsules of Evil Alien Energy were collected, Mega Man brought them back to Dr. Light in hopes that his creator could analyze them. However, Duo, having been brought to Light's laboratory for repairs, sensed the Evil Alien Energy and destroyed it before breaking out and heading for the source of the power-Wily's tower fortress. Pursuing the mysterious robot, Mega Man also arrived at the tower, only to be attacked by a massive robot powered by Evil Alien Energy. Duo arrived and destroyed the robot with a single blow, before explaining the nature of Evil Alien Energy and his mission to Mega Man. Since Duo had to leave and destroy the Evil Alien Energy spreading around the world, Mega Man infiltrated Wily's fortress to stop his experiments with it. Along the way, he was forced to defeat Bass, who had used the energy to power himself up and fuse with Treble.

When Mega Man destroyed Wily's final machine, the Evil Alien Energy within it suddenly entered his body in an attempt to corrupt him. Duo spirited him away from the crumbling castle and managed to purge Mega Man of the energy through a combination of his own abilities and Mega Man's noble mind. With the last of the Evil Alien Energy destroyed on Earth, Duo left to find other worlds where the evil power had manifested.

A similar, but different Alien Energy makes a appearance in Mega Man 2: The Power Fighters, which is studied by Dr. Light before it was stolen by Dr. Wily. In search of new sources of alien energies, Due returns to Earth and helps Megaman in his battle against Dr. Wily. After defeating Dr. Wily, Duo collects the stolen energy. Deeming it too dangerous to let it here, he leaves Earth once more, but promising to the others to return once more.

Other media
Evil Alien Energy appears in the Rockman 8 manga.

Trivia

 * It's often speculated that this energy was the basis of the Maverick Virus, but it's unknown if there is a connection between them and the Roboenza.


 * According to the content that was in the Rockman Zero Collection official site, Dr. Light made X with a perfect virus counter-measure because of an unknown computer virus of alien origin that caused robots to become violent and riotous. The virus mentioned is believed by some to be the Evil Alien Energy. (Translation in The Mega Man Network).
 * Newer speculations say, that the Evil Alien Energy and the other are in fact Cyber Elfs. This claim is based on the observation, that it is energy with a volution on its own, making it extremely similiar to Roboenza, the Sigma Virus and its variants (Zero and Nightmare), DNA Souls and said Cyber Elfs from Megaman Zero.