Warning: The following article contains spoilers for Uncanny X-Men #20, by Matthew Rosenberg, Salvador Larroca, Guru-eFX and Joe Caramagna, on sale now.
Mutants are an endangered species in the Marvel Universe right now. Despite the best efforts of the X-Men, the global mutant population has been decimated by a series of disasters, including a plague spread around the world through the Inhumans' Terrigen Mist cloud.
With almost all of the X-Men trapped in the Age of X-Man alternate timeline, Cyclops, Wolverine and a handful of other X-Men find themselves in world where anti-mutant sentiment is worse than ever before. After the mutant-hating General Callahan orchestrated the release of a vaccine that depowered the next generation of mutants before they emerged, the X-Men made several questionable decisions in their desperation to save mutantkind.
In Uncanny X-Men #20, the X-Men have to face the consequences of their uneasy alliance with Dark Beast, a twisted mad scientist from another dimension. After learning that Dark Beast has weaponized the vaccine to make it lethal for potential mutant children, Magik summarily executed the villain.
Although Dark Beast may be another world's version of Hank McCoy, he's a far cry from the friendly blue-and-furry Beast that the X-Men know and love. Dark Beast was introduced in Scott Lobdell and Roger Cruz's X-Men: Alpha #1 at the dawn of the Age of Apocalypse, a dystopian timeline where Professor X was killed before he formed the X-Men.
Taking after his mentor, Mister Sinister, Dark Beast became a sadistic mad scientist who conducted cruel genetic experiments. With the apparent end of the Age of Apocalypse at hand, Dark Beast escaped into the main Marvel Universe in the mid-1990s.
After kidnapping Beast and taking his place on the X-Men for several months, Dark Beast revealed his true nature and battled various X-Men squads for years. When faced with a dwindling mutant global population, Dark Beast even teamed up with his Marvel Universe counterpart. However, the partnership crumbled thanks to Dark Beast's monstrous actions.
After he seemingly died, the Marvel Universe's Mister Sinister rebuilt Dark Beast and gave him a cybernetic body. When the X-Men found him a few months ago in Uncanny X-Men #13, they apprehended him and conscripted him into serving as their resident scientific genius.
Although he seemingly cured several X-Men from a Transmode Virus infection and saved Cyclops from a life-threatening injury, he was mainly focused on finding a way to neutralize Callahan's mutant vaccine, which the X-Men then spread around the world.
As a brutal sequence at the beginning of this issue revealed, Dark Beast's "cure" could kill any potential mutant who received it, which was his way of scaring parents out of giving the serum to their kids.
After Captain America and the mutant science hero Doctor Nemesis confront Cyclops about what the "cure" is doing, the X-Men confront Dark Beast, who explains his evil plan. As soon as he finishes his monologue, Magik executes him with her teleportation discs to send part of Dark Beast into the ceiling, decapitating him.
Coincidentally, Dark Beast is the second X-villain who's been decapitated in this storyline. In Uncanny X-Men #16, Joseph, a once-noble Magneto clone, was killed by the psychic ninja Kwannon after he attacked the X-Men.
While Doctor Nemesis said that he could still save the children affected by Beast's work, this has been an especially deadly era for both the X-Men and their enemies, including Shinobi Shaw and the Nasty Boys, who also died in this issue.
Despite what happens to him in this issue, Dark Beast probably isn't gone for good. With all of the unseen modifications Sinister made to his body, the villain might not need anything other than his head to survive.
While his cruelty may be as well-honed as his intellect, Dark Beast is still one of Marvel's foremost experts in genetic mutation. Because House of X and Powers of X seem set to dramatically redefine what mutants are in the Marvel Universe next month, it's likely only a matter of time until Dark Beast returns to make dark new discoveries.