WARNING: The following contains spoilers for New Mutants #21, now on sale from Marvel Comics.
While the current era of X-Men stories have focused on a united mutant community, there are still some players working against the common good and towards their own goals. One of these has been the Shadow King, whose role in New Mutants as a secret mentor has been building up momentum as he moves toward a mysterious goal. However, the young mutants of Krakoa have uncovered his machinations, and are now determined to pay him back for the pain he has secretly inflicted upon them.
New Mutants #21 (by Vita Ayala, Rod Reis, VC's Travis Lanham & Joe Caramagna) sets the stage for the New Mutants to confront Shadow King. However, it appears that the cunning villain has anticipated this response from his foes, and actually looks forward to the confrontation.
The Shadow King has been a major presence in New Mutants over the years, targeting the original team in their youth. After being granted a place on Krakoa due to the general amnesty offered to all mutants who became citizens of the island, the Shadow King seemed to put aside his hatred and need for control. However, he still manipulated the younger mutants on the island behind the scenes. He took a number of young mutants from the Wild Hunt under his wing, acting as a sinister mentor to No-Girl, Anole, Cosmar, and Rain Boy. Instructing them on how to briefly switch bodies thanks to No-Girl's abilities, they even began to experiment on taking control of husks -- mutant bodies with no life in them. This greatly concerned Scout, who attempted to talk with them about their bond to the Shadow King.
Scout's concerns were well-founded, as she was soon targeted by the Shadow King and was killed during the Hellfire Gala. Discovered by her friends, the group decided to try and force the Five to restore her even if the rule against resurrecting clones prevented them. However the Five agreed to resurrect her, arguing that Scout was her own person and had the right to live out her life as a mutant. Her friends finally agree with her suspicions about Shadow King, which are confirmed when Scout instinctively attacks Wolfsbane. Scout claims that the last thing she remembers before her death was seeing Wolfsbane and then nothing but shadows and pain. Wolfsbane has no memory of this, and comes to the conclusion that her mind had been taken over by the Shadow King.
Wolfsbane informs her friends Mirage, Karma, and Magik about what happened, confirming their suspicions regarding their friend's recent personality shifts. All of them have previous experience with the Shadow King (especially Karma, whose body was taken over and controlled by the villainous mutant), and are prepared to take the fight to him. As Magik points out, she even brings an especially powerful level of authority with her when they do confront him, due to her place on Krakoa as one of the four War Captains who can lead the mutant nation in times of crisis.
However, their work will be cut out for them. The Shadow King is one of the Marvel Universe's most dangerous psychic forces and has been capable of taking on the likes of Charles Xavier with relative ease. His experience with fighting the New Mutants leaves the possibility that they're walking into a trap -- which is also hinted at considering his sheer glee at the prospect of fighting his old foes once again. The New Mutants have a major battle in front of them, and they could hold the future of Krakoa's next generation in their hands.