After being framed by Will Magnus, the Mariner is captured by S.H.I.E.L.D. and the Judgment League Avengers. Mister X assembles a team from the ranks of the Judgment League: Avengers to free their fellow metamutant. The team is composed of Apollo, Runaway, Nightcreeper, Firebird, Mariner, Wraith and Mercury and are collectively known as JLX.
After successfully freeing Mariner, JLX flees to the safety of Atlantis, the purported origin of all metamutant kind. Before reaching their destination, the JLA catches up and a battle ensues in the ocean. While holding their own against the likes of Captain Marvel, Super-Soldier, Angel Hawk, Canary, Goliath, Hawkeye, and Dark Claw, the JLX are able to slip away after a distraction by Angel Hawk, a fellow metamutant in secret.
Upon arriving in Atlantis, Mariner is shocked to find it in ruins, and the team runs into Will Magnus, Jocasta and his metamutant hunting robots known as the Sentinels. During the fight, Mister X reveals his true identity, that of a Skrull named J'onn J'onzz and manages to defeat the Sentinels. JLX decides to remain together in the name of metamutant kind.