The beginnings of the JLX (Justice League: X-MEN) started with JLA #122, when the Mariner was framed by Will Magnus for the destruction of some Roxxon oil tankers. The Mariner went on the run, and S.H.I.E.L.D. and the Judgment League Avengers went after him. However, most of the metamutants in the JLA believed that the Mariner was innocent. They were contacted by the mysterious Mister X, who had once funded the JLA, until the JLA discovered that he had a criminal record. For unknown reasons, Dark Claw was the only metamutant on the team not contacted by Mister X.
Mister X assembled Apollo, Firebird, Nightcreeper, Mercury, Wraith, and Runaway. Together the team became known as JLX, and freed the Mariner from where the JLA had locked him away. The Mariner joined the team. After the JLX had freed the Mariner, the JLA went after them. In an epic battle shown in JLX #1, the entire JLA fought against the JLX. The battle stopped after Mister X contacted Angelhawk, informing him to fake an injury, which he did. In turn, Mister X kept Angelhawk's metamutant origins a secret.