Magik

So... is this the little girl that needed Colossus to save her from a mere tractor?

Magik was a 1984 limited series of 4 comic books, featuring the Ascended Extra Illyana Rasputin (sister of the X-Man Colossus). In X-Men #160 the team was trapped in Another Dimension ruled by the dark lord Belasco, and escaped. When they left the portal Belasco grabbed Illyana and took her from the real universe. Kitty lost her for a second, got her back... seven years older. For the X-Men it was a moment, for Illyana it was seven years.

The limited series tells what had happened in those years. Because of a time travel paradox, there was a second group of X-Men in that dimension, who got trapped while their Illyana was saved. Storm, now an old woman, became a sorcerer, and helped the newly arrived X-Men (including her younger self) to return to Earth, but could not prevent Belasco from getting Illyana and making the first of five power stones that would allow Belasco's gods to break the dimensional barriers. Storm was easily defeated, and then rescued by "Cat" (Kitty Pryde, with feline traits added by Belasco). They took her to Storm's garden, who wanted Illyana to be her apprentice, but Cat offered her to learn to use the sword and physical fight, unrelated to magic. In Belasco's castle Cat kills Nightcrawler, Belasco's servant, but fails to kill Belasco himself. He changes her even more, turning her into a complete cat, with an animal mind, and Illyana accepts Belasco's guidance, becoming his apprentice.

Some time later, Illyana's mutant power awakens: she can control the teleporting discs that are all around limbo. But, initially, she can not control their destination, which could be anywhere and anytime. She falls into limbo's past and saw an old battle of Belasco and Storm: she killed him, and became a demon like him. It was not actually him, but a figure of him, and by his murder she became a demon (it would take her several years, up to her old age, to be good again). Another disc, and Illyana returns to the castle. There, Storm fights again against Belasco, but Cat kills her from the back. Illyana kills Cat, and foils Belasco's plan with the dying Storm. This time she could summon a teleporting disc at will, and take Storm's corpse to her garden, to bury her. But then, it becomes cold and the plants begin to die: it was a magic garden, and without Storm to maintain it, it is left to become one with the rest of Limbo. To punish her, Belasco removed Illyana's power over the discs, and left her in the wild, alone. She tries, on her own, to repeat Storm's magical feats, but failed each time. Then, she changes her mind: rather than life, she tries to create a weapon. She returns to Belasco's castle and began to fight him; during the fight she became red, with horns and a demoniac tail, while Belasco gets human again.

And then, she realizes that she was about to become like him. She tossed the sword, and refused to go on fighting. Neither one being a demon anymore, Belasco left limbo, and Illyana did so as well. At that point, she reunites with the X-Men, in the scene described at the beginning.

Tropes used in Magik include:

Ascended Extra: Before this story, Illyana Rasputin was just Colossus' sister who was playing in the farm, just about to be crushed by a runaway tractor, and then saved by the mutant who can turn his body into steel. Just a supporting character in Colossus origin story, and nothing else.
Astral Projection: Storm made several
Becoming the Mask: Kitty Pryde was usually called "Kitten". With a sense or irony, Belasco gave her traits of a cat, and then turned her completely into a cat.
Cool House: Storm's magic garden surely qualifies.
Corrupt the Cutie: It's all about that
Demonic Possession
Everything's Deader with Zombies: As if things were not hard enough for Illyana, she was captured by zombies of the deceased X-Men
Face Heel Turn: Nightcrawler
Magic Is Evil: Pointed by Cat. All magic in Limbo comes from Belasco.
No One Gets Left Behind: Averted. When Illyana and Cat were running, Illyana fall to the ground, incapable to go any further. Cat was willing to leave her behind, alone against a nearby monster... forcing Illyana to stand up and run even more.
Praetorian Guard: Nightcrawler
Send Me Back: All that poor Illyana wanted all the time was to go back home to Soviet Russia, with her farmer parents. And, with one of the discs, she could... but, being much older than she was supposed to be, they did not recognize her, and shut the door in her face.
Storming the Castle: At the end of the story, Illyana captured Belasco's castle, all by herself.
That Woman is dead: Used by "Cat" when called "Kitty" by Illyana.
The Dark Side: The comic book is contemporary of the Star Wars films, and it is highly influenced by them. See the first fight to the death of Storm and Belasco: did anyone remembered Luke?
The Dragon: Sym
The Obi-Wan: Storm
Year Inside, Hour Outside: Worse than that. A mere moment in reality equals seven years in limbo.
Year Outside, Hour Inside: When she took her as her apprentice, Storm and Illyana used astral projection for some first teachings in magic. Just some minutes... and when they returned to their normal bodies, a whole year had passed.