Collects Cable (2020) #10, Children of the Atom (2021) #3, Excalibur (2019) #20, X-Men (2019) #20, Hellions (2020) #9-10. Threats multiply in the Reign of X! As Cable and his allies get closer to the secret of the missing mutant baby, a fateful reckoning draws ever closer! The origin of the Children of the Atom is revealed - but who really are these junior X-Men behind their masks? Meanwhile, an invisible threat is loose on the island of Krakoa - unseen, unheard, undetectable by any…except Excalibur. Elsewhere, one of the deadliest enemies in the history - and future - of the X-Men comes online. And when Mister Sinister goes missing, can the Hellions unravel the mystery?