Rise of the Guardians and Narnia

While exploring the ruins of a castle in Scotland Jack manages to find a portal to Narnia and runs into Jadis (White Witch) at the beginning of her hundred-year reign, Jadis decides she likes Jack and casts a spell over him to make him her slave; under the force of the spell Jack adores Jadis and does anything she says without question. When the Pevensie children arrive in Narina the enslavement spell has taken it's toll on Jack, he is no longer the free, fun loving prankster he was before, he is quiet, shy, and doesn't like to be away from Jadis' side unless she instructs him to be elsewhere, he also has a very hard time remembering anything before he met Jadis and is told by Jadis that his memories before her are not important; he wears royal-style clothes that Jadis has him wear but he is also covered in ice (Think of a cross between Icicle-Jack and Prince-Jack for those who know what those AUs are). As Jadis' power over Narnia starts to wain so does her spell over Jack, he starts to get back aspects of his old personality and some of his memories, the amount of ice covering him also gradually decreases, Jadis almost constantly keeps Jack at her side to keep the spell strong. Jadis sends Jack back to her castle before the final battle to keep him safe, away from Jadis Jack regains himself more quickly but is still under her influence until Aslan, Lucy and Susan come to the castle and Aslan uses his own power to fully release Jack from Jadis' hold. Back to his old self Jack goes with Aslan, Lucy, Susan and the freed Narnians from Jadis' castle to help out at the battle.

After the battle is over and the Pevensie children become the kings and queens of Narnia Jack is invited to stay in the castle by Lucy, Jack agrees because he cannot remember the way back home. Before Aslan leaves he tells Jack that he will eventually have to return to his home to fulfil his destiny there, when Jack asks if he would be able to return to Narnia after he leaves Aslan leaves him with a cryptic message which basically translates out to maybe. Years later the Pevensies go hunting and end up finding the wardrobe again and leaving Narnia, at the same time Jack finds the portal he used to get to Narnia and goes through it to get home. On Earth Jack finds the Pevensie children, who believe in him due to Narnia, Jack doesn't return to Narnia even when the Pevensie children get pulled these again, The Pevensies last longer than usual believers and believe in Jack when they reach adulthood but one by one they forget he's real and no long see him, Lucy in the only one who believes in Jack until the end.