Rockslide

Santo Vaccarro was sent to the Xavier Institute where he befriended Hellion and the would-be Hellions Training Squad. He was originally advised by Iceman, but was selected by Emma Frost to be part of her prized Hellions Squad. Santo and the rest of the Hellions went on to win the Field Day Tournament and were declared the best squad at the end of the school year.

During the summer vacation, Julian, from a well-to-do background, invited his friends to his home. The Hellions ran into trouble quickly, as his and Mercury's appearances along with Dust's dress disturbed people at the airport. After a brief struggle, the group was allowed to board, and made their way to Julian's home in California. Soon, the team encountered the Kingmaker, from whom they each received a trial wish. Santo's wish was to become a World-class Champion in superhuman wrestling. However, when the Hellions eventually refused a permanent deal with the Kingmaker, the Kingmaker shattered Santo with a laser blast. Julian used his telekinesis to piece Rockslide back together, and together the Hellions defeated the Kingmaker.

Soon after returning to the school after the vacation, the Scarlet Witch created the reality known as the House of M. In this reality, Santo was once again a champion superhuman wrestler. After the effects of M-Day, he was one of the few students who didn't lose their powers. The depowered students and staff were sent back to their homes. One bus was bombed by anti-mutant religious zealot Reverend William Stryker, and Santo's former teammate and friend Tag was among those killed. The X-Men held a funeral for those students whose parents would not accept them, and Santo reflected upon how he had "failed" by not being able to save those killed.

With the mutant population drastically decreased, the government sent the Sentinel O*N*E* Squad to watch over the school, which began housing as many remaining mutants as would take refuge. All of the remaining students were placed by Emma Frost into an all-out brawl, and the ones deemed to be the best were to be assigned to become a group of in-training X-Men. Santo made the team and began training to become a X-Man.

William Stryker continued his terrorist attacks against the school. Santo's teammate Elixir ended Stryker's plans by killing him. The New X-Men, with the help of Prodigy, then made the connection between Stryker and Nimrod. The team leader, Surge, then decided that the team would find and destroy the robot. When the team confronted Nimrod, Rockslide was obliterated in the battle. Hellion and Mercury tried desperately to awaken and to piece him back together, but Rockslide's remains were initially unresponsive. Thankfully, even in his shattered form he was able to survive, and was finally put back together, only to become larger and more rugged than his previous form. Rockslide was later seen talking to Match and Anole about their abilities and how useful or non-useful they would be if they joined the New X-Men team, indicating Match and Anole may be possible candidates for admission onto the team. He was at the memorial service for all the students lost in Stryker's attack on the institute.

Santo later became a citizen of the mutant nation of Krakoa. He attended the celebration of Krakoa being officially recognized as a nation. He was seen standing near Match at the party on Krakoa while Wolverine handed Gorgon a beer.

Santo later befriended a mutant who was from Arakko in the forest of Krakoa, Summoner, who he played a traditional Arakko game with, which reveals weakness in each player. Growing closer, he went with Summoner to Arakko to rescue Unus, only to be betrayed and killed by Summoner, by destroying his energy form. When the Five attempted to resurrect Santo, they learned, to their horror, that because he died in Otherworld, the real Santo perished as well as Otherworld is a nexus to the multiverse. The copies of Santo within Cerebro were overwritten in all backup helmets and the version that was resurrected was instead a combination of other Santos from across the multiverse. In order to honour his death, Polaris used his remains to build the portal for the Ten of Swords challenge.