Gate is a Reploid scientist and the primary antagonist of Mega Man X6. He was a former colleague and friend of Alia, the female Reploid who later became a Navigator for the Maverick Hunters. The two of them used to conduct research on Reploid DNA-Souls together, creating several highly advanced Reploids whose DNA could not be analysed. Gate's work was met with disdain and jealousy and many of his colleagues conspired to discredit him, sabotaging his research and having his Reploids labelled as Maverick and destroyed.
Two weeks after the fall of the Eurasia Colony and the environmental devastation of Earth, Gate conducted an investigation of the Eurasia crash site. There, he discovered a piece of debris that contained an abnormal energy signature. Further analysis would reveal that the fragment came from the fallen Maverick Hunter Zero and the energy within it was a remnant of the Zero Virus.
Gate studied the fragment for a week, but in that time he became corrupted by the virus and turned Maverick. Seeing the virus as his key to achieving unlimited power, Gate - with the aid of the mysterious scientist Isoc - created a new virus derived from Zero's viral code: the Nightmare Virus. He then used his research to resurrect his former retired creations, organising them into a group he would dub the Nightmare Investigators.
Gate and Isoc then came up with a plan to use Zero as a scapegoat for creating a new society of selected, powerful Reploids; independent from humanity, in an ideal state, led by Gate. To do this, he created a discoloured, apparently insane copy of Zero, called the Zero Nightmare, which was then publicly blamed for the recent Maverick attacks by Isoc. Isoc encouraged Reploids all over the planet to join the Nightmare Investigators to hunt down and destroy the Zero Nightmare to restore peace.
Eventually, Gate would contact the Maverick Hunters upon their victory over his creations, inviting X and Zero (if found by X after the destruction of the Zero Nightmare) to challenge him. He later revealed that he didn't set up all this on his own, but with the help of Zero's DNA. In order to gather and analyse even more data about the two ancient robots, Gate challenged X and Zero to battle. By utilizing all the data he had analysed by now, Gate managed to make his golden battle armour virtually invincible against all attacks, except his own if they were repelled against him. X and Zero managed to find this weakness and defeated him, leaving him damaged and immobile. Gate, however, refused to give up. Although he didn't want to do it, Gate unleashed his final trump card: a revived (yet incomplete and incoherent) Sigma. Unfortunately for him, however, Sigma refused to acknowledge Gate's part in his resurrection, nor needing him for anything, and killed him. After Sigma had been defeated, X returned to the remains of Gate's laboratory, salvaging his body because he was unable to leave him there as he used to be Alia's friend. Yet, he had been severely damaged. Alia was given the choice of what to do with Gate, repairing him or otherwise; however, it was never made clear and his fate remains unknown.
Gate is a devoted researcher with a cold and sarcastic attitude. In order to achieve his goals, he's willing to do everything necessary to get what he wants. During his time with the research team, unlike Alia, he broke research protocols by making his creations unanalysable, causing him to become a social outcast. He became bitter and filled with hatred when his creations were destroyed by his very own colleagues, especially because Alia (who's often speculated to have felt romantic feelings for him) was part of the conspiracy. Like many of the villains in the Mega Man X series, Gate desires a Reploid government under his leadership, and will gain it by any means necessary.
Gate believes that the best programs are completely unanalysable, which is why he is so fascinated by X and Zero, and why he values the sample of Zero's DNA that he obtained so highly.
When Gate is fought in his laboratory he discards his normal lab coat for golden armour. He flies freely around the room while X and Zero are forced to manoeuvre on a series of scattered platforms, while abusing his complete immunity to standard weapons.
- Nightmare Hole: Gate flings a series of different coloured "gates" at them. Each colour of gate does a different thing, and they can each be destroyed to hurt Gate with their scattering fragments.
- Nightmare Enemy: Gate will fire off a giant purple orb that will generate a Nightmare Virus.
- Nightmare Move: Gate will alternate between trying to ram the hunters off their precarious perches.
- Nightmare Strike: Gate will also perform a wide strike that can destroy some of the platforms.