Loki wakes surrounded by bodies. It's surprising. Not the bodies - he remembers the fighting on Svartalfheim - but the fact that he wakes. He had not thought that he would.
Gingerly, he sits up. The wound in his chest smarts at the movement, but not as much as it should. Loki looks down and sees green light glowing on his chest, around the wound that is now much smaller than it was before. Apparently, his seidr won't let him die.
So long as he lives, Loki might as well make use of this unexpected opportunity. Thor doubtlessly thinks him dead, or he wouldn't have left him here. The Kursed who killed Frigga actually is dead, so Loki's thirst for vengeance has been sated. The Convergence is approaching, and Loki has no doubt that Malekith has plans to use the Aether during it, but Thor can handle that. Loki has other concerns.
Loki has other vengeance to wreak.
He finds the battered ship they stole from Asgard and uses simple spells to smooth out the dents and polish the scratches. It takes more effort than it should, and he can feel the healing in his chest stutter as he redirects his seidr away from it, but it is necessary. He redirects another trickle of seidr into a glamour to make him look like of one of the Einherjar. He has no doubt that Odin sent warriors to check Svartalfheim, even if he hasn't seen any, and he will be sure that they bring back news of his death.
Returning to Asgard via one of his secret paths is easy enough. Loki is able to enter the palace without confrontation, looking as he does. It's ridiculously simple to reach the throne room, and Odin.
"Forgive me, my liege," he says as he steps up. "I've returned from the Dark World with news."
Odin turns his head, only barely paying attention. "Thor?"
Loki looks away, trying to hide his bitterness. Of course Odin asks after Thor first, of course he doesn't give a damn about his second, disgraced son-
"There was no sign of Thor, or the weapon," he says. "But…"
Odin turns, as Loki hoped he would. Drama has always been Loki's purview. "What?" Odin asks.
Loki steps forward. "We found a body," he says. A part of him is aching to see how Odin will react to the words, but he doesn't dare hope that Odin will actually care.
"Loki," Odin says.
At first, Loki thinks he's been found out, but the look on Odin's face isn't the anger Loki would expect if that were the case. Instead, his expression looks like… grief?
And then Odin crumples to the ground.
Loki rushes forward, unable to stop himself. He sends out a whip of seidr to slow Odin's fall, then holds him in his lap as he tries to figure out what happened.
When he figures it out, it's with a sick sense of irony. The Odinsleep always does seem to happen at the least convenient of times for him. What is he supposed to do now?
"My liege!" a voice yells from down the hall, just out of eyesight. Loki panics, drapes a spell over Odin to hide him, and then wraps himself in a glamour that looks like Odin. The still-healing wound in his chest protests the amount of magic he's using, but this is necessary. Someone needs to rule Asgard during the Convergence, and apparently Odin cannot.
"My liege!" Tyr runs forward, bowing as he approaches. "My liege, the Convergence is beginning!"
Loki tries to look appropriately solemn. "We will do what we can," he says. He uses more magic than he probably should when he teleports Odin away to his room, and he's forced to lean on what's left of the throne. Tyr takes a step forward, as if to help support him, but he doesn't look particularly surprised at the moment of weakness. Apparently, the Odinsleep that Odin just succumbed to is not an unexpected one. Loki will use that to his advantage. After the Convergence ends, he'll place Odin in his bed and leave Asgard, and everyone will assume that he simply slipped into the Odinsleep when things grew calm once more.
Except Odin will wake knowing that he fell into the Odinsleep before the Convergence, whereas the people of Asgard will have seen him, or at least someone in his place, leading them through it. Except Frigga (the mere name still brings Loki pain) always said that Odin could still see everything around him even in the Odinsleep, so he will know what is occurring in Asgard as he sleeps. Except this will all mean that Loki's hastily-constructed façade of death will be torn away, and he will once again be sentenced to a lifetime in an Asgardian prison. If he's lucky, at least; as an escapee and with the only person who still cared for him dead, Odin would be within his rights to order Loki's execution.
Impersonating Odin on a long-term basis wasn't his plan, but it may be the only thing Loki can do to keep his secret secure.
"My liege?" Tyr asks, taking another step forward.
Loki puts out a hand and Gungnir materializes into it. "Let us see what we can do," he says, leaning on Gungnir perhaps a little too much as he strides down the hall. Tyr follows him. The wound in Loki's chest throbs.
After the Convergence, he will feign the Odinsleep while he tends to his wound and figures out what to do with the real Odin. And then… Well, and then he'll have the whole of Asgard to rule.
He doesn't let himself smile - Odin wouldn't, and he has to pretend to be Odin - but it's not without effort. This may not have been his plan from the beginning, but Loki thinks it's a rather good one.
Now, if only the wound in his chest would stop aching with every movement, he thinks he could be truly satisfied.
Years later, on a Sakaaran ship, Thor turns to Loki. "So you didn't die on Svartalfheim after all."
"It's taken you this long to figure that out?" Loki snarks. He doesn't like thinking about Svartalfheim.
He feels a phantom pain in the scar beneath his shirt.
"That's two times I've thought you dead, brother," Thor says. "Do not torture me with a third."
That's two times I thought I would die, Loki almost says, but he swallows the words, and all he says is, "I won't."