BIOGRAPHY
Very little is known about Rockslide prior to his joining Xavier's Institute. He never mentioned his homelife, however his parents were seen during Parents Day so presumably he was accepted by his family. While at school, Rockslide started as nothing more than a muscle-bound lackey and friend of Julian Keller. His size, strength and appearance gave him an intimidating presence, even if he looked remarkably similar to a gray Thing from the Fantastic Four. Santo was quick to defend Julian and even fight his battles for him, as demonstrated during parents’ weekend, when he held back Josh Foley after he and Julian got into a brawl. However, this gruff exterior belied a goofy and direct personality. Emma Frost approached Julian and most of his friend group about becoming their new advisor. Emma claimed she only chose those students she deemed had the most potential and invited them all onto her squad, despite Rockslide’s complaints of her serving delicate French patisserie over pizza. When asked what he would want his codename to be, he decided on Rockslide, as the name Rocky would make people think of the movie. [New Mutants (2nd series) #3-10]
With friend groups firmly established at this point, it was no surprise that Santo and Julian found themselves on Emma Frost’s Hellions squad. Josh and his friends comprised the New Mutants squad under Dani Moonstar and the two squads quickly found themselves pitted in direct competition with each other in the first of many school-approved field exercises. The Hellions proved to be quite formidable and strategic in the match, with Rockslide serving as a literal rock wall, blocking off the entrance into the hedge maze 
housing the goal. He and his teammate Tag managed to stall long enough for their teammates to secure the prize and win the day.
The drama did not stop there, as one of the New Mutants Wither was forced to leave with the police for accidentally killing his father with his death touch when his powers first manifested. Julian, now named Hellion, decided to put up a stand for his fellow mutant and dragged Santo and the rest of his team to the police station with the intention of busting him out. However, the New Mutants arrived to stop them from causing an incident between the school and the authorities. Rockslide used his power to launch his fist at the group but was then incapacitated for the rest of the fight by the pheromone-emitting Wallflower, making him cry uncontrollably over “losing” his hand. [New X-Men: Academy X #1-6]
Thereafter, Rockslide mostly appeared in the background as Hellion’s friend, playing video games or skipping a teacher’s funeral to play Frisbee. At the end of the school semester, the Hellions had accumulated enough points during the field day exercises to be declared the winning squad. However, the Blob rudely interrupted their victory by attacking the school. Rockslide helped participate in a New Mutants and Hellions coordinated attack on the villain in a rare instance of the two rival squads working together. [New X-Men: Academy X #15]
Hellion invited all of his friends to his parents’ mansion in California for summer break, but the team ran into trouble at the airport when Rockslide and Mercury’s appearance alarmed security. Santo was more than willing to start a scuffle with the officers at Julian’s behest and the only reason the teens avoided detention was due to the government and lawyer connections of Julian’s parents. On the plane ride, Santo bonded with fellow Hellion member Wither but was a bit insensitive when he suggested that he could have used his killing decomposition touch to teach those guards a lesson. Upon arriving to Julian’s mansion, his parents reprimanded the boy for using their contacts and informed him they would be disinheriting him. Hellion member Dust suggested that they should leave but Santo advocated for staying in this awesome house. Sore from the way his parents treated him, Julian enlisted his team to search his parents’ offices for clues on how they had actually made their money. Eventually, they found a document containing a mysterious spell, which they performed that night to place a phone call. Despite thinking the spell amounted to nothing, a man called the Kingmaker arrived the next morning. [New X-Men: Hellions #1]
The Kingmaker explained that he could grant all of them one wish but, upon Dust expressing reservations on what would be owed later, he said he would leave unless all six of them agreed to take his deal. Julian suggested a demonstration was in order and Rockslide volunteered to be the first wish granted. Soon after, Santo was living his dream of being in a professional wrestling match. This was a super-powered no holds barred, “real” wrestling league and Rockslide soon won his first victory, with the Kingmaker guaranteeing his rise over the season to the title match. 
Santo basked in the cheers of his name on the crowd. Meanwhile, Brian had a curious wish in that he wanted to protégé with the Kingmaker to do what he did. He explained that with his powers to make somebody “It” he wanted to be able to make his friends Julian and Santo the “It” people in making their dreams come true. Towards this goal, Brian was acting as Santo’s wrestling manager to ensure his rise to the top. With all of this success, Rockslide remarked that calling the Kingmaker was the best thing they had ever done. [New X-Men: Hellions #2]
However, the Kingmaker was not doing this all for no compensation, and his payment had come due. The favor that he was asking for, should they wish to keep their gifts, was to travel to a genetics facility and prevent the theft of a powerful project from two mercenaries, Paladin and Diamondback. While the team were able to take the item from the pair initially, the mercenaries 
experience soon turned the tide against the Hellions, such as Paladin throwing Rockslide’s own fist back into his face. Ultimately, Julian used his telekinesis to take down the two foes and recover the briefcase but not before Diamondback admitted that SHIELD had hired them. Despite reservations from the rest of the team about being used, Julian was adamant about them holding up their end of the deal with the Kingmaker, even after discovering the briefcase contained a bio-weapon. [New X-Men: Hellions #3]
This turned out to be a ploy by Julian to get the Kingmaker to tear up their contracts before 
handing over the weapon. Once the Kingmaker did so, Julian ordered his team to take back the weapon. Of course, the Kingmaker was not going to go down easily, as he had an arsenal of weapons and powers at his disposal, one of which he used to seemingly disintegrate Rockslide into rubble. Julian managed to telekinetically reassemble Santo so that he could use his strength to hold down the Kingmaker until the authorities arrived. Despite his ban from the wrestling league, Wither tried cheering up Rockslide by saying that at least he would go down as having a perfect 1-0 winning record. Santo admitted that it was a dumb wish anyway and apologized to Wither about losing his chance to control his death touch. [New X-Men: Hellions #4]
After the event known as the Decimation in which most of the mutant population was depowered, Rockslide was one of the approximately 198 mutants that retained his powers. Possibly due to his durability, he was one of a few students to occasionally assist one of the main X-Men teams. This included fighting against the arrival of the Office of National Emergency’s Sentinels and the return of Apocalypse. He even took a punch from the Horsemen War during one assault on the institute and was around during the invasion of the Children of the Vault. [X-Men (2nd series) #177-179, 185-186, 192]
Santo was not the most sensitive of classmates when it came to the trauma visited upon his fellow student body in the wake of the Decimation, as demonstrated by his having slept through the initial chaos and offering unwise help like pretending to run away from his friend Brian to simulate his lost powers. In order to get their minds off the craziness, David, the now depowered and former team leader of the New Mutants, took his friends into the Danger Cave, which could simulate past X-Men battles. Rockslide was eager to fight in these simulations but complained 
about being relegated to the role of Colossus in every scenario. Soon, Emma Frost decided that every powered student left at the institute should be placed in a battle royale to determine who would make the official X-Men team in training. At the start of the battle, Rockslide attacked Julian, who admonished him and told them the Hellions needed to stick together. Rockslide took several other students down but lost his arm to the clone of Wolverine, X-23. Whether through his merit or because he was a student of Emma Frost, Rockslide made the final line-up of seven New X-Men. [New X-Men (2nd series) #20-23]
Any sense of jubilation from this victory was quickly tarnished by one of the worst tragedies to occur at the institute. Emma had decided to send all of the depowered students away from the school and, once the several dozen children had boarded the bus, a mutant-hating group called the Purifiers, led by Reverend William Stryker, blew up the vehicle with a rocket-propelled grenade. Every one of Rockslide’s former classmates perished from the explosion, including his friend Brian, all while Santo stood in shocked disbelief unable to move. At the resulting funeral, Santo cried while remembering with shame his inaction. The New X-Men failed in their task to take down Colossus during a ruthless training session in the danger room, with Rockslide even thrown through a wall by the steel-skinned X-Man. This training for life and death situations soon came in handy when the Purifiers enacted their raid on the mansion to exterminate them all. Another few students were unfortunately killed, but Rockslide and the New X-Men were able to hold off the intruders long enough for their teammate Elixir to put an end to Stryker permanently. [New X-Men (2nd series) #24-27]
The threat continued past Stryker, as the power behind the man turned out to be an alternate timeline’s future mutant hunting sentinel Nimrod. The damaged sentinel had escaped its captivity and teleported to Dallas to find the mutant mechanical genius Forge in order to blackmail him into repairing itself. Meanwhile, the Institute received a visitor from Ms. Marvel of the Avengers, who wanted to offer condolences but also ask her former X-Men allies to consider registering for the new Superhuman Registration Act. Rockslide awkwardly tried flirting with “the hottest Avenger ever” but his teammate Mercury called out his creepiness. When team leader Surge’s Forge-designed gauntlets broadcasted a call for help, the rest of the X-Men failed to take the young students seriously. Therefore, while the older mutants all flew off to Africa for a wedding, the New X-Men devised a plan to escape the school on a Blackbird jet and fly to Dallas to save Forge. Nimrod managed to blast the plane out of the sky but the team survived and busted into the 
compound to start fighting controlled security bots. When Nimrod himself managed to finish his repairs and join the fight, he exploded the building, nearly killing everyone if not for the telekinesis of Hellion and Rockslide holding up a huge amount of rubble. Nimrod attacked once again and would have killed Hellion, if not for the heroic sacrifice of Rockslide jumping in front of the energy blast, vowing not to stand by again while his friends perished. Thought dead by his teammates, with Mercury in particular devastated, they managed to send Nimrod to the past and were overjoyed when Rockslide was able to reform from the pile of rubble that was his former body into an aesthetically more jagged appearance. His personality remained grating and, despite Mercury telling the other students to be nice to Santo, his jokes quickly started to wear on them. [New X-Men (2nd series) #28-32]
Santo adjusted quickly to his new bulkier and rougher exterior, not even putting much thought into it. He did not seem much perturbed at the disappearance of his teammates Mercury and X-23 and instead was much more interested in the news that there was a Young Avengers. He was determined to one day beat up their “big” guy Hulkling. He did help in the retrieval mission and sarcastically remarked how "awesome" Kitty Pryde’s phasing was as he actually took down bad guys. [New X-Men (2nd series) #33-36] Soon after, the New X-Men squad became involved when Exodus and his Acolytes infiltrated the mansion. They were targeting various items and people that had knowledge of the future, including the student with pre-cognition powers Blindfold and the diaries of the deceased pre-cog Destiny. When they came upon Blindfold, surrounded by her friends, she appeared to be recently deceased. Rockslide was the first to try to punch Exodus but it amounted to little before the X-Men arrived to take on the powerful foes. [X-Men (2nd series) #201-202]
One particularly spooky night around the fireplace, Rockslide regaled his fellow students with embellished tales of his periphery exploits with the main X-Men team. When called out, he asked the others to tell a better story and Blindfold began spouting a cryptic prophecy about Illyana Rasputin and her former master Belasco that student Anole quickly recognized as currently happening or near future events. Despite Santo being unimpressed with the story and a little creeped out by Blindfold, her words turned into reality when the ground beneath their feet opened 
up and dragged all of the children into Limbo. Belasco immediately captured most of the residents of the house, while Rockslide and the other kids he was with were pulled to a different section of Limbo. Santo did a poor job taking lead in the situation as the only member of the New X-Men. Instead, Anole stepped up to direct the terrified group of mutants when a horde of demons showed up to capture them. Rockslide attempted to shoot out his arms but, given the weird nature of Limbo, instead exploded. With all hope seemingly lost, Illyana showed up to rescue them. [New X-Men (2nd series) #37-38]
As Illyana captured and tortured some of Santo’s friends in an attempt to forge a new soulsword, an enraged Rockslide reformed out of hellfire magma and rocks to protect them from her. The new, colossal form made him resistant to magic and Santo quickly pinned Illyana, despite his attraction to her, but Anole stopped him from killing her. Rockslide had reservations with Anole’s plan to trust Illyana by having her use fellow student Pixie to form a bloodstone in order to teach her a teleportation spell, but ultimately the squad was able to pull off the plan and attack Belasco’s stronghold. Rockslide distracted Belasco by attacking him directly, while the others helped free the other captured students and teachers, leading to victory. Illyana teleported everyone back to the repaired school and Rockslide showed some loyalty by declaring himself off the team if Cyclops did not let Anole and Pixie on the New X-Men squad. [New X-Men (2nd series) #40-41]
In some rare downtime, Beast examined Rockslide’s condition and concluded that his true power came from his body being an energy construct that could shape the earth around himself into a golem body. He suggested that Santo explode himself willingly to get rid of the Hellfire body since it prevented him from detaching his limbs as his previous body allowed. Despite some initial fears, Anole goaded him into complying by calling him a sissy and thus Rockslide was able to reform his former Rocky exterior. He was soon using this power for mischief in order to startle his fellow classmates. Despite, occasionally displaying bully-like tendencies, Santo did care for his friends. He gathered the younger, more scared students to reassure them that, even if the world were out to get them, he would protect them and make sure to go down fighting as a true X-Man. He then ruined this moment by outing Anole as gay in an attempt at further bonding, which he was cool with because it meant more chicks for him. [New X-Men (2nd series) #42-43]