The Upstarts were part of a secret competition founded by Selene, the Black Queen of the Hellfire Club, who wanted to test potential members for her own Inner Circle. Overseen by the Gamesmaster, the Upstarts would each try to kill as many mutants as possible and the Gamesmaster would award points based on the mutant's power, skills and general importance in the world. At times he would raise the value of certain mutants so that the Upstarts would all try to assassinate them. At other times Gamesmaster would also reward the death of non-mutants. To gain entry to the Upstarts competition the requirement was to kill a member of the Inner Circle of the Hellfire Club, but later members were not required to do so; usually the Gamesmaster claimed that their participation would make the game more interesting. The member with the most points at the end of the competition would win "the prize". It was never explicitly stated what the prize was (though a statement by Andrea Strucker in X-Men #4 and a notation on the back of the Upstarts' X-Men Series I trading card state that the prize was immortality), but it was inferred that the winner would gain control over the other contestants as well as gain a lot of power and influence.
Shinobi Shaw took the early lead by killing his father Sebastian Shaw. He celebrated with a group of contestants who were never seen again afterward. The time-traveler Trevor Fitzroy gained membership with the deaths of Donald Pierce and the Reavers. He demanded the ring that signified leadership of the Upstarts from Shaw, but Shaw refused, claiming that he still had more points. Fitzroy would go on to kill the Hellions, but Fabian Cortez applied for membership and immediately took first place in the competition for the death of Magneto.
The German twins Fenris tried to join the competition and gain an advantage by resurrecting Omega Red. Their plan failed though and they named only probational members by the Gamesmaster. Graydon Creed joined as well, using the moniker Tribune, and despite not succeeding killing anyone, the Gamesmaster gave him full membership. Trevor Fitzroy had met a woman in the future, named Sienna Blaze, who had told him where she would be one day. Fitzroy knew that Blaze had incredible mutant powers and told her that the Gamesmaster invited her to join the Upstarts.
Over the next few months, the Upstarts would try to kill as many mutants and other important people (like Moira MacTaggert) as possible, but with no success. In an attempt to reinvigorate the competition, the Gamesmaster started the Younghunt: the new targets were all surviving members of the New Mutants and Hellions. Instead of killing them, the Gamesmaster demanded that they should capture the targets. This competition brought the Upstarts into conflict with the New Warriors and X-Force. At the end of the game, the Upstarts had captured most of their targets, but Paige Guthrie convinced the Gamesmaster to play another game: instead of killing mutants, the Upstarts should try to find and train young mutants like herself. The Gamesmaster was intrigued and canceled the competition. The Upstarts disbanded shortly afterward.