see "A Firestar is Born" episode recap for origin
Firestar was a former X-Men member, much like Iceman. She worked with Professor Charles Xavier to harness her powers and completely control them, though she was already pretty much in completely control of them before she joined the X-Men.
It is never told why she left the X-Men, though she and Iceman left simultaneously, were attending ESU, where they met Peter Parker. The three of them changed into their superhero identities to ward off the likes of Firefly, though Spider-Man received a glimpse of their identities. Realizing they made a great team, the group decided to join forces. To seal the deal, Spider-Man revealed his secret identity to level the field. Under the title "the Spider-Friends", coined by Firestar, the trio fights crime in the city of New York, living in Peter's apartment, which doubles as a head quarters financed by Tony Stark (Iron Man).
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