Zero Nightmare

The Zero Nightmare (ゼロ ナイトメア) is an insane off-colored Nightmare copy of Zero created by Gate, through use of Zero's DNA. When he is defeated, Zero will become a playable character. He is weak to the Z-Saber.

Characteristics
The Zero Nightmare is a discolored pallet swap of Zero's X5 sprites.

Zero Nightmare uses imperfect variations of attacks used by Hunter Zero in X5, but with random shot speeds. Most notable is a delay when he swings his saber, where he holds it above his head before coming down, and his use of Genmurei Kai, a "revised" version of an attack used only by Awakening Zero. However, this variation is not instant kill, and is only one wave, rather than two. Its is also subject to the same odd randomness in speed. He can also teleport, and does so frequently in battle.

Curiously, and ironically, Zero Nightmare is actually weak to Zero's Z-Saber, causing him to flinch and cry out in pain when hit with it, after which he immediately teleports away from X to another spot. Note that this only work if X is standing when swing the Z-Saber, and if he is jumping or on a wall (either sliding down or hanging on using the Shadow Armor), Zero Nightmare will just be damaged normally.

Zero Nightmare seems to be mentally unstable, almost a botched project. At times he would ask X where Zero was, seeking him. Other times he would claim to be Zero himself, and yet other times, he would yell "BLUE LIGHT MUST KILL" among other incoherent phrases in a senseless rage. No matter what, though, X would deny his claims or snap at the "cheesy fake," and Zero Nightmare would instantly go into a rage bent on killing X, or claim X has gone Maverick and that he will retire him. These conflicting and random exchanges of dialogue seem to suggest that a particular quality that became botched, was Zero's various memories. While some memories and attack patterns seem to have remained from different periods of Zero's life, the clone was not complete in any respect, and was therefore easy for X to see through as a forgery of his longtime friend.

History
Zero Nightmare was created by Gate and used by Isoc and High Max's investigation teams to justify their existence. The two claimed to want to get to the bottom of the Nightmares, but in reality, both used the fradulent claim of Zero being on a rampage for Gate's advantage--fully knowing that Gate was the true perpertrator. Created from Zero's DNA, Zero Nightmare seemed to retain some of Zero's memories, but at the same time sought out the real Zero, for unknown reasons. The investigators were to have the public believe that Zero had fallen under the influence of the dreaded Nightmare, but Zero Nightmare had simply been created that way as nothing more than a faux to give credibility to the claim. The legitimate Zero decided to be kept out of sight as the Zero Nightmare tarnished his name, and only revealed himself once X had disposed of the clone.

Power and Abilities
Zero Nightmare has the same exact arsenal as of Zero from Mega Man X5, using both his Z-Saber and Z-Buster to attacks, only with limited movepool and subsequent speed.

Note: With the exception of Denharei (電刃零), Shin Messenkou (真滅閃光) and Genmurei Kai (幻夢零改), none of these attack names are official.
 * Teleportation: Zero Nightmare can warp around the room in a dashing stance.
 * Z-Saber Slash: Zero Nightmare hold his Z-Saber up and after approximately half a second, he swings it.
 * Z-Buster Shots: Zero Nightmare shoots two shots that go straight ahead.
 * Thousand Shots: Zero Nightmare shoots a large barrage of charge shots from his Z-Buster.
 * Denharei: Zero Nightmare launches an energy wave that is semi-homing from his saber after using Z-Buster.
 * Shin Messenkou: Zero Nightmare punches the ground, making several energy projectiles fly up from the floor.
 * Genmurei Kai: Zero Nightmare attacks with a weaker version of Awakening Zero's final attack, firing off single giant energy waves at varying speeds.

Trivia

 * If a battle between the real Zero and the Zero Nightmare is triggered through the use of a cheating device, the Zero Nightmare will use the quotes of High Max, assumably because the dialogue was never programmed for an exchange between Zero and the Zero Nightmare, resulting in the game loading the next available dialogue in its programming: that of High Max.
 * One very notable line that Zero Nightmare says upon encountering him, is "WHERE IS ZERO? WHERE IS HE HIDING? A BLUE ROBOT. ENEMY OF ZERO...KILL YOU!" It is interesting in that while searching for Zero, he identifies X as Zero's enemy. It is possible that along with some memories from Zero, he may possibly have inherited some of Zero's memory of his mission to destroy X from the Maverick Virus. This is also supported by his imperfect usage of Genmurei, an attack used only by Awakening Zero in X5. The conflict of memories could be the cause for his mental instability.
 * On the other hand with the aforementioned quote, Zero Nightmare's dialogue may not in fact be referencing X at all, as the stated quote could be a reference to yet another one of Zero's original memories: His original purpose of destroying Mega Man, as programmed by Dr. Wily. Considering the insane nature Zero Nightmare exhibits, it is highly plausible to suggest that Zero Nightmare confused X with Megaman. This is also supported by Zero's terminology, describing X as "A BLUE ROBOT." To call X a robot, is rather peculiar because this term was replaced by "reploid" long ago, giving merit to the believe that Zero Nightmare did in fact reference Megaman by mistake.