A/N: Movie-verse, starts pre-movie, possible movie spoilers—including the post-credits scene. Also, "Sky-Walker" is one of Loki's names from the Norse myths; the name has nothing to do with Star Wars.

The first time Loki stepped between worlds on his own, it was mostly an accident.

Loki loved the Bifröst. He didn't like its guardian—Loki had trouble liking anyone he couldn't trick, setting aside the pranks Heimdall had ruined—but the bridge itself was his favorite part of Asgard. Partially because it meant he was going somewhere else, somewhere new with new people to read, new tricks to light the pages. But that was only a bit, and had it been the only thing, he would not have loved the Bifröst—would have associated the bridge too much with all-seeing Heimdall to see it as more than a pretty means to an end.

But Loki loved the feeling.

He was a little disappointed how few others noticed, that first time, not that the dissatisfaction could tamp down his exhilaration at having felt it. Loki had glanced around at the others—expecting Thor to be fully focused on the quest ahead rather than the feeling, but for someone else to have noticed. The only other person who looked at all affected was Sif, who nodded at him briefly, registering only surprise on her face before she focused and chased after the running Thor. Loki couldn't believe she wasn't awed by it, having clearly focused enough to have felt it, even if the other oafs hadn't—

"Loki!"

Loki ran after Thor's call by reflex alone, reluctantly leaving the entranced feeling behind when he caught up to his brother, Sif, and the Three. When they came back from that trip—whatever it was, because the point had been more about the thrill of leaving Asgard than anything else, so that was the memory—Loki looked at Sif. She didn't even look surprised this time, just…normal. Thor was grinning, but that was because he finally had a story to tell father that Odin didn't already know. The Three looked…bored. Maybe a little tired. Loki shook his head in disbelief and walked quietly behind and to the right of Thor—for even then Loki knew he was very much the second son, though the fact hadn't begun to bother him yet.

Loki wanted to see everything. The trickster would have found a way to join all of Thor's adventures one way or another, but rapidly found that he was much less use in a blade-to-blade fight than he needed to be to survive most of the first son's trips. And, like it or not, until and if Odin allowed Loki to travel on his own, Thor's adventures were the way to travel.

Truly. The. No one else seemed interested in the ideas of a place but Sif, who fought and thought better for learning about other cultures, but who stopped coming along the first time she missed an adventure with Thor. Loki missed her company, even when he could travel alone. She liked the Bifrösttoo—Loki saw that as soon as he was not so surprised by the experience himself. She tried to hide the joy, for one reason or another, but the trickster was no stranger to hiding emotions. Especially on the Bifröst, where he learned to hide his own love the first time he traveled back—no point in showing Heimdall so obviously, after all.

Loki watched Sif hide her happiness, and slowly learned to read all her emotions as easily as he read Thor's.

Once, on Midgard, he had read her aloud, and she had blushed beneath a tree with pink blossoms. Loki leaned in close; Sif moved slightly and, as was her wont, acted. When they started, neither thought too much. As they moved together, neither could.

Upon their return to Asgard, Sif found that she had missed an adventure Thor bragged about all evening, and that was the end of that little chapter. Loki tried not to think about that afternoon.

He still remembers her scent, the light through the trees playing dappled magic on her skin, and the only words either of them had spoken in that place, though not which one of the two breathed them.

"Better than the Bifröst."

Loki accepted, quite early on, that simple physical combat was never going to be his strong suit. He looked for ways to use his other studies to his advantage.

The first use he found was in reading people. Loki had already been reading the basics—hesitation (time to hit), watching someone recalculate when he had thrown them off (satisfying; one more nudge), and going wild (strength is useless; focus on agility and gaps in their defense). But he found with a little practice he could see the movements people made when they were about to move. Most prepare for a punch like this, a jab like this, a feint like this; watch carefully and every step becomes clear before the other person even finishes planning.

Swiftly after that, he started using magic. First came illusions—ones of himself were the best, since his opponent had no idea where to hit, but others helped. Green balls of light made to look like fireballs, though some, like Thor, stopped dodging those rather quickly. Loki found it worked much better when he interspersed them with actual green fireballs.

Soon enough, Loki could fight just as well as Thor, though their respective styles meant Sif or Thor still had a better than even chance of beating him when they sparred. Loki worked much better when he didn't need to worry about injuring his opponent.

The long and the short of it was that Loki traveled by the Bifröst as much as anyone. The trickster always found something new to revel in, and hid the emotion every time but the first.

So when Thor walked the bridge without the trickster, Loki was understandably—if not outwardly—upset. Thor always ran off first, and Loki always fixed everything. That Thor should get to go alone before Loki… Loki did not like the word "fair," given how often he had been accused of fighting unfairly simply because he used the skills granted him, but he did consider this situation unfair.

Loki walked—at a perfectly normal speed, with a slightly bored expression on his face—to the library. He was not angry. He did, however, call a bit of invisibility about him so that, should he appear angry, no one would notice.

Rather, he tried to call a bit of invisibility. Magic required focus, and seething under a forcibly blank exterior was taking its toll on the illusionist's focus.

Loki continued walking, and anyone who hadn't noticed the subtle hand gesture would have no idea he had just failed to cast a spell.

What was it? Loki had never had trouble focusing, so had often read under his desk while the teacher went over meditation techniques. He had paid enough attention to be able to repeat the teacher's last few sentences back verbatim, and no more.

"When you have trouble focusing on a spell, the first thing to remember is that distractions happen to everyone. Regardless of whether the strike against your focus is life-changing or trivial, there is no need to be ashamed of it. Being ashamed will only add to your distraction. Secondly, admit what the problem is."

Loki took a deep breath. I am jealous of my brother because I believe he has father's favor. There. Once said, it already had less power.

"Breathe deeply and try to accept it. Whether you can or not, try to focus on something else."

I appear to have the breathing down, Loki thought with unexamined humor that quirked his lips. Now, another focus…

The afternoon with Sif was out. That was distracting in its own way, and he could never get the water cold enough. Any memory with his brother or father was also out, since those would lead back to the original distraction.

A snatch of the time with Sif came to his mind, unbidden, "Better than the Bifröst."

Bifröst.

Loki took the feeling, not the first time, too tinged with surprise to fully appreciate, nor the last time, when he had been running and had his focus split between illusions and not showing Heimdall, but maybe the third time.

Loki took a deep breath in through his nose and out through his mouth, then wrapped that beautiful feeling of being in the universe, of sliding between like sneaking through passages to spy on his parents, or watch someone train, and then being called over, welcome and joining…

Why not? It wasn't like anyone would hear him if he put a name to the feeling. The Bifröst was a sense of belonging. Home.

He wrapped that sense around him, called up his magic—

And stepped straight into the boughs of Yggdrasil.