
As a result of House of M, Magik has been resurrected and the demon Belasco has been slaughtering leaders across dimensions to find her. This included taking Limbo back from Amanda Sefton, who fell back to Earth at the end of the last arc. Next, he pulls the students from Earth into Limbo and pits them against an army of demons—trying to get them to tell him where Illyana is…

…It’s Hell, so he seems to kill them but they’re not really dead.
The students don’t know where Illyana is, but another group of them find themselves face-to-face with her in a different part of Limbo.

Majik tells them that to defeat Belasco, she needs a new soulsword, and Pixie agrees to make the sacrifice. But before it’s complete, her team-mates interrupt the process—leaving Pixie with a souldagger. This also seems to bring Illyana out of her demonic rage (not sure why), and she helps bring the team to Belasco’s castle.
Meanwhile on Earth, the rest of the team finds Amanda Sefton, who has the ability to bring them to Limbo.
Everyone’s together now for a big fight. The Stepford Cuckoos psychically attack Belasco and then Pixie stabs him with the soul dagger. Illyana then destroys him, and Illyana is once again queen of Limbo.

She sends the team, including Colossus, back to Earth—without restoring Pixie’s stolen soul.
So that’s the big picture. There are also lots of nice, smaller moments in this story arc that really can only be appreciated by reading the story. Also, the last two issues are shared with installments from the Endangered Species epic, which is covered in a separate article.