Magma hailed from the fictional country of Nova Roma (New Rome), a colony of the Roman Republic reportedly founded shortly after the death of Julius Caesar in 44 BC. The colony was hidden in modern Brazil and was ruled until recently by the immortal mutant sorceress Selene. Amara was the daughter of Lucius Antonius Aquilla. He was presumably a member of the historical gens Antonia which claimed descent from Anton, son of Hercules.
A faction of the city’s Inca population attempted to transform the republic into an imperial state and a dark cult following the Black Priestess was regularly sacrificing young girls in a pit of fire in some caves beneath Nova Roma. Senator Aquilla was the leader of the opposition to this faction. Fearing for his daughters safety, he sent his daughter Amara to live in the jungles outside Nova Roma, disguised as an Indian. Later, the senator discovered that the Black Priestess was actually the immortal mutant Selene, wife of Senator Marcus Domitius Gallio, the leader of the Imperial faction.
Amara remained in hiding for years until she was captured by the New Mutants, who were on an expedition in the Amazon jungle. They learned of her disguise, but then both Amara and the New Mutants were captured by soldiers of Nova Roma and imprisoned. Now held prisoner by Selene, Amara was to be sacrificed. Selene used her mutant powers to drain Amara's life energy into her own body. The New Mutant named Mirage attacked Selene. This distraction caused Selene to release Amara from her control, but Selene knocked Amara into the pit of lava.
Somehow, rather than harming Amara, her immersion in the lava awakened her latent mutant powers. Together, Amara, with her new-found powers, and the New Mutants defeated Selene and helped thwart Senator Gallio's attempt to kill Senator Aquilla and seize power. Amara was instructed to go to the United States with the New Mutants and there learn about modern civilization. Amara did so reluctantly and became a member of the New Mutants under the code-name Magma.
At first Magma experienced culture shock, however she soon got a handle of modern civilization, including such things as computers and electricity. She also made quick progress in the use of her powers, being able to melt tunnels into the ground with the walls cooling down in mere seconds.
At a Hellfire Club event, Magma recognized her grandmother, "many times removed" in a statue depicting the ancient lunar deity Selene. Selene approached her to claim having been both the model for the statue and the ancestor in question. Magma refused to believe her claim.
Amara later left the New Mutants and joined the Hellions, and then returned to South America with the Hellion member called Empath, who she had romantic feelings for. Amara sensed something was different about her homeland and its people but could not discern what was worrying her.
Later, all of the remaining members of the Hellions were killed by Trevor Fitzroy. Warpath, joined by Firestar and Cannonball, who were all once members of the Hellions, went to South America to tell Amara and Empath of the death of their former teammates. While there, they discovered that Amara and all the people of this city had been living a lie. The city had not been founded by ancient Roman settlers. Instead, it was populated by the kidnapped and mind-wiped victims of Selene. She had created the city as a testament to the times she loved most and desperately wanted to relive. With Selene gone from the area, the spell had started to fade. Empath had tried to prolong the scenario as, for the first time in his life, he was happy. The people of Nova Roma started to regain their memories and Amara was told that her real name was Allison Crestmere and that she was a mutant of British descent.
Later still, both Magma and Empath were kidnapped by the mutant twins Fenris, a plot that was part of an elaborate and deadly game organized by the villainous Gamesmaster. They were rescued by the team X-Force (formerly, the New Mutants). Afterwards, Magma decided to leave Empath and her friends to search for her family in England.
Alison was not seen again until her appearance in King Bedlam's new Hellions. He called her a "British exile," so it seemed that she did not rebuild her old life as planned. How she came to join him is unknown. However, when King Bedlam unleashed the Armageddon Man on the U.S., Magma did not leave with him, and helped X-Force shut down a nuclear reactor and stop the Armageddon Man.
Magma later turned up among a group of mutants captured and crucified on the front lawn of Xavier’s mansion by the Church of Humanity. Magma was among the few victims saved from certain death by quick transfusion of Archangel's new healing-factor-laced blood. However, Magma remained in a coma for a time.
A few weeks later, students Josh Foley and Julian Keller found out about Amara and decided to wake her up with Josh's healing abilities. Magma awoke and let out a power blast that nearly demolished the entire wing, then ran away. She joined up with the "X-Treme" X-Men team in California and reunited with her old friend Cannonball, then ran into Sunspot and Empath as well. Magma no longer thought of herself as Allison and was instead completely back to her Amara persona. How and why this change occurred, and which identity was the true one, is unknown. Amara helped the X-Men fight and temporarily defeat Elias Bogan and his telepath, though she reduced the LA X-Corporation headquarters to slag while doing it.
While vacationing in Guadeloupe, she found a new boyfriend. Antonio Argent was a mutant with almost the same powers as Magma. While on a date in the magma of a volcano, the "House of M consequence" took his mutant powers away. He combusted in the twinkling of an eye. His death temporarily drove her insane causing her to make the volcano erupt and attack a nearby town. She was later apprehended by Empath and brought to the Xavier Institute where she shared a tent with Skids and Outlaw. She was also being manipulated emotionally by the mutant Johnny Dee who was infatuated with her. Because of previous experience with being emotionally controlled, she incorrectly blamed Empath who denied her accusations.
Geokinesis: can psionically control the movement of the tectonic plates within the Earth's crust within limited areas, probably no less than a radius of a few city blocks. Within this area she can create small or large earthquakes by psionically affecting the Earth's crust.
Pyrokinesis: can create flames and project blasts of heat that do not contain any molten rock. However, she apparently prefers to fire magma blasts rather than simple heat blasts, perhaps because the magma blasts have a solid impact that can knock down a target. The highest level of heat that Magma can generate is not yet known, but it is believed that she can reach at least 850° Fahrenheit or higher.
Magma Manipulation: can psionically cause magma, or molten rock, from far beneath Earth's surface to rise to and break through the surface, forming miniature volcanoes. can also telekinetically project fiery blasts of magma at targets. Apparently she does so by turning nearby rock molten and then telekinetically hurling it at her target.
Magma possesses the normal human strength of a woman of her age, height, and build who engages in moderate regular exercise.
Magma's costume and clothing are made from unstable molecules so that they will not be harmed by the tremendous heat she generates.