I do not own Thor or any of the characters. Fair warning, I don't know the names of any specific places. I'll try my best though.
Left Behind
Sif sat up and looked around. A long rest felt good, especially after the Dark Elves incident, as S.H.I.E.L.D. had so happily called the near-destruction of Earth at the hands of the Dark Elves. She and the others had largely recovered from what injuries they had received during it while Thor was still trying to recover from the damage the Aether had done to him. It would be a while yet before he could do much of anything, despite having been a full month since Malakith had died.
After a few moments, her mind drifted back to her dream. Always the same, at least for the past few weeks. She replayed the dream in her mind for several moments before sighing and standing, forcing it away. She needed to avoid those thoughts, at least for now. She made her way through the halls of the palace, soon reaching the medical room that King Odin had once occupied while Thor was banished. Thor himself now rested in the bed, sleeping soundly with Eir checking his wounds. After a moment she finished and nodded to Sif as she left. Sif sat in the chair beside Thor and he turned his head toward her, smiling.
"You look tired," Thor smiled.
"I haven't been sleeping well," Sif admitted. "I'm sure I'll be fine."
"You're not sleeping?" Thor questioned, a worried look taking over his features.
"I am," Sif assured him. "But I find that rest eludes me regardless of how long I sleep, which usually isn't much anyway."
Thor nodded thoughtfully then asked, "Nightmares?"
Sif smiled and shook her head. Thor would undoubtedly guess until she told him but She wasn't ready for him to know, assuming he didn't already. She never had been overly skilled at lying or keeping secrets.
"Hogun?" Thor questioned.
"No no," Sif laughed. "It's not them."
"Is it me?" Thor questioned.
"Alright Thor," Eir interrupted. "Your wounds are healed enough that I should be able to close the rest. It might take a while and it will likely hurt, but you should be able to handle it. It won't be any worse than fighting can be."
Thor nodded and Eir began. Within seconds, Thor had his eyes squeezed shut, his teeth clamped shut, and Was struggling to hold still. After a moment, Sif reached out and took his hand, allowing him to squeeze hers. It didn't seem to help much but it helped a bit. Finally, after over an hour, Eir finished and left and Thor passed out. Sif left the room and found Eir waiting.
"Thor should wake up after a bit," Eir stated. "You will have to tell him that Heimdall was looking for him."
Sif nodded then asked, "Where are you off to?"
"I'm needed elsewhere," Eir stated simply.
Sif watched her walk away then sighed and left, heading to meet the others at the bar they were currently relieving of all of its wine and assorted alcoholic beverages.
"Sif!" Volstagg shouted happily seeing her enter. "Join us! Have a drink!"
"No, thank you," Sif smiled sitting down. "Eir finished healing Thor. He should be up and about soon. Has anyone seen Heimdall today?"
"No," Hogun replied. "Why?"
"Apparently he wants to talk to Thor when he wakes up and I was hoping someone knew why," Sif sighed.
"Maybe he has some news about that human," Fandral suggested. "Maybe she dumped him. You'd be pretty happy about that wouldn't you?"
"W-what do you mean?" Sif questioned, already blushing slightly.
"There you are," Thor interrupted walking over and sitting down. "I wondered where you went. Getting drunk already?"
"She won't drink with us," Volstagg complained.
"I will," Thor smiled.
"First you have to go see Heimdall," Sif stated standing. "And since you just got up and probably can't even swing Mjolnir, I'm going with you, in case there's a fight."
"Fine," Thor sighed. "I'll be back for that drink. And I can too fight still!"
He and Sif left and headed to the Bifrost, and found Heimdall waiting, and unhappy.
"Are you okay?" Thor questioned.
"I am," Heimdall nodded, "Earth is not."
"What's going on?" Thor questioned.
"Something is freezing the Earth," Heimdall stated.
"Send us," Thor ordered.
"I cannot," Heimdall stated. "If you go, you die. I'm sorry."
"Send us, or bring the humans here!" Thor ordered. "As many as you can."
"I cannot," Heimdall stated.
"Why?" Thor questioned.
"Because I can no longer see Earth," Heimdall stated. "It is gone."
"Gone?" Thor questioned. "Gone how?"
"I do not...I found it," Heimdall stated, voice grave.
"Send us," Thor ordered.
"Very well," Heimdall nodded. "And I am sorry, in advance."
Heimdall drove his sword into the control mechanism and activated the Bifrost. Then, he sent Sif and Thor to the surface of the Earth, except it was no Earth he remembered. This one was barren and white. Frozen solid but more like everything had been turned into ice, not covered in it. They were standing about fifty feet from Dr. Selvig's house. Thor instantly rushed through the door, smashing it when he tried to kick it open. What he saw, was what he was afraid of. Eric, Darcy, Ian, and Jane all frozen in place. They were all looking at a computer screen that was now a clear sheet of ice. None had seen whatever happened coming. They were all the same, transparent ice sculptures.
"No," Thor breathed falling to his knees. "Jane. Eric. No."
"Thor," Sif muttered kneeling beside him. "I'm so sorry Thor."
"This is my fault," Thor stated. "I should have been here. I should have protected them."
"You couldn't have been here for them even if you had known," Sif stated. "And there's no way you could have protected them. You'd be dead too if you were here. Thor there is nothing you could have done."
After a moment, Thor nodded and stood just as the Warriors Three arrived behind them.
"What the Hell happened here?" Volstagg questioned. "Everything's ice."
"And so is everyone," Sif stated. "We need to get back. Before something bad happens."
Just then, the ground began to crack and they all sprinted back to the point they had arrived at. Heimdall activated the Bifrost but just before they left, a blue hand shot out of the ground and grabbed Fandral, dragging him back into the ground just as the others left. The moment Thor arrived, he ordered Heimdall to send him back.
"I cannot," Heimdall stated. "I used too much power rescuing you four. The Bifrost shattered the Earth. I'm sorry. He's gone."
Thor took an involuntary step backward while Hogun and Volstagg sat down hard, both in a state of shock. Sif didn't take it much better but knelt beside Thor, wrapping an arm around him, as he had also entered a state of shock.
"If it helps, it was a quick death," Heimdall stated. "He felt no pain."
No one answered. After a time, Sif managed to convince them to find somewhere else to grieve. Finally, they agreed and went to the room in the palace they usually met at. Once there, they were all lost in their memories.