Black Zero

Black Zero (also known as Hyper Zero) is a forbidden deity which can be summoned by Zeroes through a certain ritual that implies sacrificing scraps, which will end up in Black Zero taking over the summoner's body for a limited time, granting him amazing powers for a limited time.

The Ritual
To initiate the ritual, the Zero requires 10 scraps in his possession. Then, Zero will gain the ability to charge their saber by holding down the ATTACK button. Should Zero release the button after reaching the pink level, he will freeze in place and start to channel the dark energy, eventually turning black as Black Zero possessed his body.

As long as the takeover is in effect, the receptacle will be granted the following buffs:
 * Strength up: the receptacle's damage output will be increased by 50%.
 * Impact slash: all of the receptacle's attacks will cause the opponent to flinch, even those which previously didn't.
 * Godspeed: the receptacle will see his movement speed increase greatly.
 * Unstoppable: the receptacle will be immunized to flinching from attacks.

The body takeover lasts 10 seconds, after which the Zero has to let Black Zero go. Some zeroes have tried to keep Black Zero longer than the usual 10 seconds, but the ones who succeed end up with major physical/mental scars, if they even survive.

The ritual can be started only once per life.

The Awakening
The Ritual was discovered in version 5.0, which was probably due to the awakening of based Vile. At the time, getting possessed by Black Zero granted even greater powers than it does now: The damage output was increased by 2x instead of 1.5x, the takeover would fully refill the Zero's health, and the ritual could be started multiple times per life. These buffs, notably the damage output, made Black Zero the most feared opponent for anyone with a brain, being able to shred to pieces even a Ride Armor. Black Zero quickly acquired a status of all-powerful god of Megaman X Online.

There is one imposter among us!
Later in 6.x versions, Axl players found out that an Axl could disguise himself as Zero and start the ritual! However, Black Zero soon found out about this sacrilege, and in version 7.0, decided to sacrifice a part of his powers in order to be able to see through Axl's masquerade.

Conclusion
Black Zero may not be as powerful now as he was before, but he is still incredibly powerful, and an opponent to watch for. He still lives on as the god of Megaman X Online.