Illyana Rasputin, aka Magik, is a deadly sorceress and ruler of the demonic realm of Limbo in addition to being a powerful member of the X-Men, but she wasn't always this way. Illyana was once a frightened little girl, terrified of Limbo's monsters and of her own potential for evil magic. This background is what causes Magik to empathize with a young mutant named Sapna who the X-Men rescue from danger in Extraordinary X-Men #1 (by Jeff Lemire, Humberto Ramos, Victor Olazaba, Edgar Delgado and VC's Joe Caramagna). Sapna demonstrates a unique connection to Limbo and its demons, gleaning information about the realm that was hidden from Magik, as well as formidable magical powers. The X-Men's resident magic user begins training Sapna to better control her magic, but their relationship ends up taking a tragic turn for the worse.
Sapna's magical potential attracts a powerful, evil force that possesses her and intends to use her to destroy the world. When Magik learns of this, she realizes that she has no choice but to kill her student. Although Sapna is innocent, there is no way to destroy the force possessing her without ending her life as well. Magik agonizes over this decision, searching in vain for an alternative, but finally goes through with killing the innocent mutant and feels horribly guilty afterwards.
To end the life of any child is obviously upsetting, but Magik is particularly vexed because of how much Sapna reminds her of her younger self. Like Sapna, Magik was manipulated by malevolent forces to cause great destruction when she was a child. Belasco, the former ruler of Limbo, had attempted to corrupt Magik's soul, but was only partly successful. Later, the demons S'ym and N'astirh tricked Magik into surrendering to her darker side in the classic "Inferno" storyline, resulting in Magik being de-aged. If things had gone a little differently for Magik, her fate could have been very similar to Sapna's.
Now that the X-Men have the power to resurrect mutants on Krakoa, it is possible for Sapna to be brought back to life. Magik could insist that the Five resurrect Sapna, thereby atoning for the murder she was forced to commit. With Sapna alive again, Magik could resume training her and ensure that Sapna became strong enough to fend off any more enemies intent on possessing her. Although it wouldn't undo the murder Magik committed, it would allow Sapna a second chance at life and help Magik alleviate some of her guilt.
Sapna could also prove to be a significant ally to Magik in an upcoming conflict regarding Limbo. In New Mutants #25 (by Vita Ayala, Rod Reis and VC's Travis Lanham), Magik and Madelyne Pryor will clash over which one of them is the true ruler of Limbo. Given Sapna's connection to Limbo and her intuitive understanding of the realm, she could be of great help to Magik in this fight. Sapna's support could be what is needed for Illyana to assert her rule over Limbo once and for all.
The X-Men's newfound ability to resurrect deceased mutants has allowed them to rectify many past mistakes that resulted in the tragic deaths of teammates and innocents. Magik was unable to stop the force possessing Sapna without also killing her, but the Krakoan resurrections mean that Sapna could be given a chance at new life while also providing the mutants with a much needed ally in their upcoming struggles.