WARNING: The following contains spoilers for Marauders #17 by Gerry Duggan, Matteo Lolli, Edgar Delgado & VC's Cory Petit, on sale now.
The Fenris Twins are two of the X-Men's most twisted enemies, mutant murderers who were raised to swear by the dark beliefs of their twisted father. Even in the age of peace that Krakoa has provided, it appears that the pair still want fresh mutant blood on their hands -- and they found the perfect place to try and get it.
The Fenris Twins have found a home watching the mutants who volunteer to go through the Crucible -- with the villainous pair even offering to take part in the battles so they can sate their appetite to kill other mutants.
The Crucible remains a fundamental part of Krakoan culture, even with Apocalypse no longer on the island nation following the events of X of Swords. The ritualistic combat allows a depowered mutant to engage in a battle to the death against an empowered opponent. If they die with honor, then they can be resurrected by the Five with their powers intact. Silver Samurai hosts the program in Apocalypse's absence and volunteers for combat if no one joins the mutant in the ring. However, there are two additional volunteers -- the Fenris Twins, who are revealed to be eagerly waiting for the chance to kill a mutant and not be punished for it.
Luckily, Callisto's chosen opponent -- Storm -- arrives on the scene, keeping the Fenris Twins and Silver Samurai from having to kill Callisto. This leaves the Fenris Twins disappointed, as they haven't gotten to kill anyone since coming to Krakoa and becoming the Black Knights of the Hellfire Trading Company. However, this also isn't lost on the other mutants present at the Crucible -- with many giving the pair ugly looks while Callisto's fellow Morlock Masque insults the twins to their faces.
The Fenris Twins -- Andreas and Andrea von Strucker -- grew up to be white supremacists like their father Wolfgang von Strucker, as well as a distinct hatred for the X-Men and their diverse allies like Storm and Magneto -- the latter of whom appeared to kill their father. The Fenris Twins would turn their casual murderous nature into a sport when they joined the Upstarts, a group of wealthy and despicable villains who turned hunting mutants into a competition. Even after their time in the Upstarts, the pair continued to hunt other mutants, seemingly until the period of unity brought about by Krakoa gave them the incentive to curb their more violent tendencies.
Notably, an incarnation of the Strucker family -- largely divorced from their twisted forms from their original incarnations in the Marvel Universe -- was among the central heroes of The Gifted, the live-action Fox series based on the X-Men. It seems that the series hasn't had an impact on how the Fenris Twins will be portrayed on Earth-616, as they are still clearly the murderous villains they once were. Just because they're trying to follow the rules doesn't change who they are, or how Krakoa perceives them.
Callisto notes that if the pair of them try to join her in the Crucible, she'll fight even harder to kill them -- invalidating the entire reason she's here. It'll be interesting to see if the Fenris Twins will continue to be a constant at the Crucible, offering their "services" to mutants who want to die so they can be reborn. With something like the Crucible now defined as a part of Krakoa even without Apocalypse, it might be worth having some mutants around who are willing to do the dirty work of the contest.