Xero is a member of Bolverk Squad and one of the four main protagonists of Xionic Madness.
Xionic Madness 1
Xero is first seen cleaning his sword when Omega was logging the mission's operatives. He will then have to fight along with Omega towards the heliport and to Askads and Karys location. Omega and Xero are ambushed by BIO INT soldiers and a heavily armed helicopter and then an A.T.D (anti tank dragon). After destroying the A.T.D, the team finally reunites and move towards XV. Xero has to carry Kary because she is exhausted because of the explosion she had to create to finish off the infected beings. Xero is last seen at the animation's ending telling Omega to catch up later.
Xionic Madness 1.5
Xero is scarcely seen in 1.5, but he is seen spliting in half some BIO INT soldiers and then threating some BIO INT scientists. He carries Kary all the way to the building's core, where Kary would be fully recharged and Xero had to plant the N8. Next he hacks into the main computer to find about his past. He learns he was built by a man called Chief Charles Smith, posibly one of the scientists he had slaughtered. He also read there was an upgrade for him in a containment room. The upgrade would finally allow him to use firearms. Xero is last seen in his brand new suit. Then he disapeared while Kary was charging, just before she recieved an upgrade left by Askad for herself.
Xionic Madness 2
In Xionic Madness 2, Xero slaughters BIO INT soldiers as well as Red and Green spies. He fights XV spawn, and at one point, kills one with its own tail.. He fights BIO INT helicopters and specialized troopers called Interceptors. He is last seen carrying Omega with his new flight ability, while he is briefing Headquarters about the mission's result. The Overseer (possibly Bolverk) also sends a message to Kary, which neither Omega nor Xero hear. It suggests Kary may betray them in the future.
Xionic Madness 3
In Xionic Madness 3, Omega and Xero are stripped of their armor after being captured by Kary. Their new armor they get is tied in directly to their bodies, allowing them to have greater speed and power. Some weapons are locked out shorty after getting this new Vertebral armour (later renamed Cervical Armor). They must kill to unlock further weapons and powers. After killing waves of enemies, Omega arives at the train station. After a battle with soldiers, flying enemies, and a artillery cannon, Xero meets at the train station for their ride. After unlocking all of their new weapons, robotic clones of them are sent to kill them. Having knowledge of all of the weapons they've used, Xero and Omega are forced to use their Longinus Kifes, and blow the entire city up.
Xionic Madness 4
Kary breaks off from the Overseer's orders, and kills him in the process. She gives away her plan to live forever. Kary wants to kill everyone to absorb their power to power her core. After blasting Xero into a building, the fight begins. Kary is taken down extremly easily, so they get suspicious. It turns out she used to energy to make a clone, to "play around" with them before killing them. With Xero and Omega, and the combo of close quarters combat and long-ranged fighting, Kary is forced to use her shields. After being backed into a wall, Kary uses her new-found powers to revive the soldiers that Xero and Omega killed as zombies, before sending them at Xero and Omega.
to be added
At the end, Xero became older, he still have the scars from the fight with Kary, he was shown speaking with his apprentice Enid at first. It was shown that The New World Order founded their location, Xero and Enid prepared for the fight, Xero knew it will be his last battle before his own demise, since the XV virus will finally bring him down, before the battle, he told Enid that she have to live on, carry on their work, to shut down their organization and called the New Order. At the after credit, it was shown Enid watching an old picture of Bolverk Squad, including Omega, Kary, Askard, and Xero, Xero wasn't visible at the time, and was no where to be seen, it is believe that he died after the battle, since Enid was seemingly standing on a battlefield.