Maria Callasantos and her three siblings, Lucia, Matteo, and Carolina, grew up poor and abandoned by their father. One of Maria's only joys was in keeping the pigeons on their rooftops as pets.
When her youngest sister, Carolina, was found dead from falling down a staircase, Lucia always wondered if Maria had pushed her, since Maria hated Carolina, blaming her for their father's desertion. Later, when their mother's boyfriend, Harry Bellinger, tried to rape Lucia, Maria's power emerged in anger, and she killed him. Nevertheless, her mother was furious, killing Maria's pigeons in return, and Maria, again in anger, killed her mother. There was no place for Lucia and Maria now-- no place but the streets. With Lucia's own mutant powers emerging, the two found refuge with the underground Morlocks.
Calling herself Feral, she refused to join Masque's army of Morlocks, fleeing to the X-Mansion. She agreed to join the New Mutants in return for their help in taking down Masque, and the team soon after became X-Force. Feral served a long tenure with X-Force, joining them on all their early adventures, including one that brought her into conflict with Lucia (now, Thornn) when Masque's Morlocks teamed up with the Brotherhood of Evil Mutants. However, Feral's naturally ferocious nature brought her into conflict with her teammates on many occasions, most notably the time she nearly eviscerated Cannonball during a training exercise.
At one point, X-Force came into conflict with the Mutant Liberation Front (MLF), a terrorist organization that had kidnapped the government official and anti-mutant activist Henry Peter Gyrich. The MLF's leader, Reignfire, convinced Feral to switch allegiances, playing up to her hatred of Gyrich and what he represented. Feral attacked Gyrich, but was stopped by Cable, and she escaped with the MLF.
Feral reappeared to confront her sister when she was captured by New York City police. Cannonball was also present and he and Lucia managed to reveal Feral's murder of Harry Bellinger and her mother. Although Feral tried to fight her way out, she was defeated and arrested.
During her time in prison, Feral discovered that she had contracted the mutant-killing Legacy Virus. She escaped from prison and joined other Legacy Virus victims who were focused on finding a cure. Feral attempted to forcibly steal the High Evolutionary's Isotope E, which was believed a possible vaccine. They were stopped by the guardians of the Evolutionary's base, the Knights of Wundagore, and apparently disbanded. (More recently, a cure for the virus was discovered and released into the air, presumably ending the threat of the virus forever.)
Feral later reappeared as a member of the New Hellions, led by the mutant known as King Bedlam. X-Force confronted the New Hellions on behalf of one of their new members, Jesse Bedlam, and during the confrontation, Feral seriously wounded X-Force member Siryn by slashing her vocal cords, an injury that left Siryn powerless and requiring a long recovery.
Maria has since falled victim to the events of House of M|M-Day and has been stripped of her mutant powers. However, more recently, Maria and her sister had their feline appearances restored, although their powers remained suppressed. While in her cat-like-form the villain Sabretooth brutally attacked Maria. Her injuries resulted in her death.
Recently, Feral was revived with an alien techno organic virus.