When Masque usurped control of the Morlocks and changed Callisto's appearance that of a beautiful woman, she met an amnesiac Colossus and fell in love. Knowing she had to free the Morlocks, this Callisto sought out help from NY's own Dr Strange before the Morlocks could attack her again. Dr Strange was not in this realm at the time, however Morgan Le Fay had been watching Callisto try to approach the Sanctum Santorum. Unknown to Callisto or Masque, at this time the Darkhold was hidden in the Morlock tunnels, having been given to a mutant by the High Evolutionary who sent the book off to America to be hidden. Morgan Le Fay, desperate to get ahold of the Darkhold approaches Callisto to "help" her overthrow Masque, since she sees Callisto as less of a threat and an easy way to possess the book. Obsessed with vanity, Le Fay offers two magic swords for Callisto to free the Morlocks in trade of her now repaired eye (Le Fay can't bear Callisto's perfect beauty). With only revenge in mind, Callisto agrees.
To cause a full distraction to make her theft as easy as possible, Le Fay had warned the Vampires of the Darkhold hiding in the tunnels (the Darkhold contains the Montesi Formula that threaten all vampires' existence). When Callisto, Colossus and Le Fay go underground, they discover the Morlocks and Vampires locked in a deadly fight. Just as Callisto murders Masque, Le Fay uses the chaos to her advantage, leaving Callisto and the now freed Morlocks to battle the Vampires and she absconds with the Darkhold.
Feeling the dire magical disruption, Dr Strange returns to NY and approaches Callisto and Colossus. He dispatches the Vampires and restores Colossus' memory, who decides to seek out the remaining X-Men. Strange and Callisto then set off to get the Darkhold back from Le Fay. (They then have a ridiculous 90s cross-over adventure, with Ghost Rider and Hellstrom and all those other angsty goth-ers).