With the Tesseract in hand, Loki could go anywhere.
With the Tesseract in hand, he did, flitting from one planet to the next in the blink of an eye. The first blink was enough to get him off Midgard; the second, third, and fourth enough to confound pursuit from Thanos for weeks, months, or (if he were very fortunate indeed) years; and the fifth, sixth, and seventh enough to take him beyond even Heimdall's eye (or so he could hope, for to be beyond Heimdall's reach was to be beyond Odin's).
After the thirteenth jump to the thirteenth planet, Loki found a quiet corner in a quiet cave on a quiet continent that had not seen sentient life in a millennium or three. There, he undid his bonds, and removed his muzzle, so that he could turn his prize over in his hands, and truly look into its depths.
At first, he meant only to gloat. At having it, when no one else did; at being where they were not, despite having been in chains mere minutes ago. At the stroke of luck he hadn't dared to imagine for himself, when it had been so clear he was to be returned to Asgard in those same chains, to receive whatever passed for judgement from Odin.
Except. When he had looked into the Tesseract for long enough, he saw something. A whisper, a shadow. There was something very different about it than there had been even a few hours ago, when he'd still had it, and things had been going so well.
"What's this?" he asked, and looked further, deeper.
Whispers and shadows, shadows and whispers. It took only a little effort to discover the Tesseract was older than it should have been, only a little more to learn it had been somewhere it had never been the last time Loki had had it. There was a flaw in it some forty years old. It was something he would have seen easily, if it had been there before.
He dug deeper, looking in and in. Shadows and whispers, whispers and shadows. They didn't want to give up their secrets...but now that Loki knew there were secrets, he had to have them. Had to have everything, to know everything about the Tesseract, now that it was his to use.
In the end, what he found was something more fantastic than he would ever have dared suspect. The Tesseract had been gone from this reality entirely for a period of days, and had then been returned. The tale it told was fantastic and strange, a cacophony of images and impressions Loki barely followed, filled as they were with people and events he did not recognize. All the Reality Stones had been together there, it seemed, pulled from his own reality and from others; they had been used to destroy Thanos and his forces, in that reality and every other, in the blink of an eye; and they'd been used before that to...
To...
Bring something, someone back. Loki could tell that much...but why that action had been needed was veiled to him. He could see, after he looked longer and longer still, that what had been undone had been done in the first place by another set of stones. An older set of stones. Older by how many years was difficult to say, but the longer and the harder he looked, the more Loki thought they could not have been even a century older. At moments, the veil came close enough to lifting that he could almost see, almost...
If all Loki had wanted a few hours ago was to depart Midgard freely, now all he wanted was to know. He pushed and he pushed, called on spell after spell, practically begged for it to tell him, to spill its secrets into his ears as easily as it had been given up to him in the first place.
The days were long, on that planet. Some thirty hours after he'd arrived, the sun finally went down. When it did, so did Loki, tucking the Tesseract into one of his pocket dimensions before bedding down with a head that ached much too much to even think about dealing with his stomach, which was empty.
When he woke, it was still dark...but the blue glow of the Tesseract beat back the night, as he looked and looked and looked some more for whatever answer might be found.
This time, rested, and his sleeping mind having reflected upon the problem, he soon came upon a possible answer, a way to grasp the knowledge he sought. If the Tesseract he held knew where its other had been, then there was no reason Loki couldn't know where his other had been...for one of the things that was most clear in the cube's murky depths was that he'd had it at least one other time. He'd had it, and if the circumstances under which he'd had it were shrouded, there was a greater connection there than there had been to the rest of what he'd almost seen. All he had to do was to concentrate on that connection, to craft a spell that claimed the right to know so clearly that such claim could not be denied.
Finally, the way was clear to him.
But there was a complication. The Tesseract held its secrets tightly, but if this one was to be released, it was clear they would all be. There was no way to do this subtly, by channeling all the knowledge of that other reality through himself alone. No, if he dredged the knowledge he desired up from out of the depths, the knowledge would go everywhere, affect nearly everyone.
Not for a moment did Loki consider staying his hand. What chaos there would be, if everyone on every world was forced to contend with a second set of memories. Even if they were less severe for those who hadn't been involved with the Stones in any reality, it was the ones who had been who deserved it. They wouldn't know if the new memories were false, or if they were true; only Loki would know, and would be free to move among them with his more complete knowledge, and with it to sow even greater mischief. What a panacea that would be, after his last few years. How glorious a revenge for all who had wronged him.
"Do it," he said, and the Tesseract glowed bluer than ever before, sending out pulse after pulse of power, from a lonely planet on the outskirts of the galaxy to everywhere else...
And when it was done, it shattered in Loki's hands, and he fell once more into the dark.
*
When Loki woke, he was halved, or doubled, in a confusion that left him curled in the dark, hands clawing at his temples. They battled inside his head, two realities, two sets of pasts. He didn't have the control he'd expected; he had no control at all. In the end, when the pieces finally decided to fit together, it was a reconciliation he would or would not have chosen, but had had no say in.
He remembered both paths, so clearly. He remembered everything. Yesterday, he had been in New York, on Midgard...
And yesterday, he had been by Thor's side as they watched Asgard burn, in a move that had been Loki's doing to Thor's bidding. Before that, there had been the battle of the Bifrost, and before that, Sakaar. Before that Hela, come from Odin's death, and before that Loki had ruled Asgard in Odin's image, and before that...
The memories had come so quickly and the Loki who'd lived them had been so changed, it seemed a wonder he'd lived through the melding.
It was bright again, outside the cave. No telling how long he'd writhed around on the floor.
He looked to the side, and saw the Space Stone, lying on the ground. Revulsion clawed at his belly, climbed into his throat: He'd taken it from the vault, when he'd gone to set the fire that would bring Asgard to ashes. He'd taken it, and he'd given it up for Thor's sake...and then died, at Thanos's hand.
Half of him wanted to rage, to say he'd never give up anything so precious for that...that buffoon who still claimed to be his brother. The other half of him wanted...wanted...
"Heimdall," he said, and if half of him still wished to think he was out of Heimdall's reach, the other half hoped even more desperately to have been wrong, "where is Thor, at the moment?"
"Still on Midgard," came the answer, albeit slowly...and when it came, it was labored, almost pained. As if Heimdall, too, had been in the throes.
Half of Loki wanted to reach down, to pick up the Space Stone and tuck it into another pocket dimension before Heimdall spirited him away. The other half of him never wanted to see it again. For a moment, he hesitated. Then he stuffed his hands into his pockets, and they formed themselves into fists, and that was fine, he'd been of two minds before, and often, for his whole life, for both his lives. How different could this be?
"Heimdall, take me to him, if you would," he said, and if in that last moment he reached for the Stone after all, and only fell short because if Heimdall's words were labored, his compliance was not...
Well, no one else ever needed to know how close he'd come, now did they?
*
The streets of New York were indeed chaos, though it was hard to say how much of it was related to the Chitauri and how much to Loki's latest, greatest mischief. At least three-fourths of Loki didn't care, for the half that had decided to reap it in the first place was now too apprehensive about being back here to properly appreciate the rest.
Heimdall hadn't set him down at Thor's precise location, but he was still easy enough to find: Sitting on a curb some three blocks down from Loki's landing place, with his head in his hands.
"Brother," Loki said.
Thor looked up. He looked strange, without the eyepatch or the gaping lack it had covered; and the conflict that twisted around inside Loki burned clearly in Thor's face, as well. He looked thunderous, murderous; at the same time, there was a hope in his two good eyes that made Loki ache, in a way only half of him recognized.
"What have you done?" Thor said, and at the same time stood and loomed over Loki, half-menacing and half...
There was hope there, still, as he searched Loki's face. There was grief there, too...but not a new grief. He'd lived, then, Thor. In that other reality. Half of Loki wanted to rage about how unfair it was. The other half was glad (though perhaps slightly ironically). The dichotomy was starting to feel normal, a natural extension of the way he'd always been unable to ever quite settle on just what he wanted.
When Thor came forward and embraced him, both Loki's halves screamed a little until he managed to extricate himself.
"Brother," Loki repeated, when he was once more out of arms' reach...and ignored the half of him that denied it, and always would. "Don't you think we should go back?"
He peered at Thor's face as he said it. Saw when it hit Thor again, both halves of him: Asgard had been gone, the vast majority of its people with it...but it wasn't gone now. Asgard still stood. Their mother still lived. Odin, as well. Who knew how long either would remain true, when all Asgard's enemies surely remembered, too. Perhaps their memories would be fainter, would fade away like ghosts. Perhaps they wouldn't. There was really no telling.
"...Yes. Yes, I think that would be best," Thor said, then called for Heimdall.
Moments later, they were home. The spires of Asgard were visible ahead of them, waiting. So was the future, and whatever it would bring.