In the spirit of clearing things up: This follows a vague pattern with my other Avengers series in that this is (oh god) an AU in which he had about as much control as Clint and Selvig.
Also I have a few deadlines coming up so the next chapter might be in a fortnight, not next week.
It started off as a fairly normal Friday evening in the Avengers Tower, as much as anything could be normal for a building full of off-duty super heroes. Although they all had their own floors, they'd all mostly taken to using the communal areas on nights like this.
Pepper, Natasha, Steve and Sam were sat on one of the sofas playing Mario Kart while Tony complained about not being allowed by the others to play after sulking for a week the last time he lost. Clint was sat on the floor in front of Natasha, leant back against her legs, probably asleep by now. He'd only got back from his most recent mission a few hours ago, even if he wouldn't specify who he was working for now.
Thor and Jane were curled up at one end of the other sofa, having only lived in the tower since Jane's visa had ended in England a few weeks ago, and Bruce was sat at the other, heading the same way as Clint. It was getting late and the scientist was halfway there already after a long week working on various projects, mostly ones Tony had asked him to help on for Stark Industries. Tony would undoubtedly wake him up as soon as he'd finished whining about the game, but until then Bruce intended to make the most of his few minutes of peace. The sound of the heavy rain outside was relaxing, somehow reaching his ears over Steve's surprisingly colourful cursing when Natasha Blue-Shelled him.
There was a thunderclap somewhere close and Bruce looked up out of the window just as it exploded with lightning.
The unnatural brightness burnt a shape into his retinas, a silhouette of two figures in the centre of the explosion, and Bruce blinked quickly to try and remove it as the same two came towards the door.
"What the fuck-"
Bruce's voice was drowned out by one of the window shattering under the blow from… was that a sword? He turned to the others and saw Natasha, Clint and Steve stood up in defensive stances, the two assassins pointing guns at the newcomers.
"Thor." A voice like an earthquake rumbled.
"Heimdall!" Their resident demigod stood up quickly, a grin on his face until he saw the grim expression on the other man's, almost hidden under his huge, gold helmet. So this was the Gatekeeper from Thor's battle stories, always there to get Thor and his warriors out of trouble just in the nick of time. Bruce didn't know what he'd expected, but the huge, muscular demigod with golden armour and dark skin hadn't been it. Guiltily, he realised he'd expected everyone on Asgard to be white, with the same vaguely Nordic features as Thor.
As Thor got closer, his expression of innocent concern turning darker, to anger with a rare but genuine fear. "What-"
"Later."
Thor narrowed his eyes but gave a sharp nod.
Heimdall cleared off Tony's bar with a sweep of one arm and lay the figure he'd been carrying down on its surface.
"I understand that you are a doctor?" He said, looking at Bruce for the first time.
Bruce hesitated, frozen in place by those eyes, pure gold but filled with something much harder. It was easy to forget that Thor wasn't actually human, but Heimdall was ancient and something far more than a prince. Bruce finally forced himself to look away, knowing that that golden gaze was something he never wanted to fall into again.
"Yeah." He said finally.
"Can you help him?"
Bruce looked down and nearly froze all over again. Lying on the table, unconscious and even paler than the last time Bruce had seen him, was Loki. Although most of his body was caked with blood and dirt, Bruce could tell there was some kind of serious damage to his face, although he couldn't imagine what it could have been caused by.
"That's-"
"Loki, yes. Can you help him?" Heimdall repeated.
"I... I have no idea. We have to get him downstairs for me to even find out."
Heimdall nodded and lifted Loki's lifeless form from the table with a lot of apparent care but very little effort, striding confidently to the elevator with Bruce. Thor moved to follow them but the Gatekeeper looked him in the eyes. "Not yet."
"My brother-"
"Is unconscious and still losing blood." Bruce interrupted, more sharply than he'd intended to. "I need to take a look at him before he stops having enough blood left to lose."
Natasha took a step forward, giving Thor's arm a reassuring pat as she moved past him. "You need a hand, doc?"
Bruce's eyes quickly flickered over to Tony, still sat on the sofa in the exact same position he'd been in just before the gods broke through the window. He was having an anxiety attack or a flashback or something. Pepper had noticed and was doing her best to get him out of it, but it was unlikely Bruce's closest friend on the team would be much help here. He nodded quickly and Natasha slid into the lift with them, swiftly giving JARVIS the instructions for the floor in case the AI had missed anything.
As they the med bay, Bruce found himself thanking god they left the room fully prepared for a patient in case a mission went bad or there was an emergency.
If this wasn't an emergency, Bruce didn't know what was.
"Put him on there." Bruce said, gesturing to the examination table at the other side of the room.
Heimdall nodded and laid Loki on it with as much care as he could, and started unbuckling the blood-streaked gold vambraces. Bruce's eyes were drawn to the ritual, unable to look away from his muscular forearms until the god tilted his head questioningly.
Bruce coughed, looking away quickly. "Any of that blood yours?"
Heimdall shook his head. "This is all his."
Natasha produced a knife from her sleeve and slit open Loki's thin shirt without another word from Bruce. She narrowed her eyes as she assessed the damage. Bruce followed her line of site and mirrored the expression; he was far from an expert on the subject, but those seemed to be pretty obvious signs of torture. Natasha had reached the same conclusion.
"If Thor's any indicator, we can't stitch him up, even with Stark tech, but I can clean up and bandage the worst if you want to get a start on-" she paused for a second, taking in the bloody mess of Loki's face. She didn't look as disgusted as Bruce felt, just kind of at a loss for words. "-whatever caused all that. Acid, maybe?"
Bruce carefully moved blood-soaked, unwashed hair away from Loki's wounds, finally getting a good look at his ruined face.
"Definitely some kind of chemical burn." Bruce cursed quietly as he cleaned more blood and grime from the burns. "Shit, what the hell have they been doing to him?"
"Are you familiar with the old myths and prophecies about our kind?" Heimdall inquired as Bruce continued to examine the wounds. The glimpse he caught of Natasha's dark expression told Bruce that she knew exactly what Heimdall was talking about, but they couldn't all be super-spies.
"Some of them." She said carefully, glancing at Bruce.
"Then specifically the ones about Loki's fate?" Heimdall prompted.
Bruce shook his head. "Not really."
"Now is not the time. Later, I will educate you on these matters."
Bruce glanced up at him over his glasses, fixing the god with a look that clearly said 'you'd better'.
He took a light out of one of the trays of medical equipment on the table next to him and pulled back the least damaged of Loki's eyelids carefully. He hissed under his breath. He had been about to check if the demigod's pupils would dilate but there was no point; Loki's eye had gone a milky white. He checked the other but that was even worse, destroyed by whatever they'd done to the rest of his face. Bruce cursed then looked up.
"Did you know about this? About his eyes?"
Heimdall nodded once.
"God." He muttered then looked up at the taller man. "We need to get him to a hospital or something. I haven't had any of the training you need to deal with this."
"He is still a wanted criminal on your realm and you are the only ones with any knowledge of Aesir."
"I don't know this much! I'm just a physicist!" Bruce protested. That wasn't strictly true; Bruce couldn't have just been a physicist to get on the research project he'd been on that indirectly got him into this mess, or to maintain his cover when he'd been in India, but this was beyond anything else he'd ever done. Loki's injuries were worse than anything he'd ever even seen on anything still alive, never mind anything he'd had to treat himself.
He felt Natasha's hand in his shoulder, bringing him out of the spiral into his mind and back to reality. He became uncomfortably aware of his high heart rate and took a deep breath. An appearance from the Other Guy was the last thing they needed right now.
"Do whatever you can. I have some contacts who should be able to help us out, but they won't be able to get here until tomorrow, absolute earliest."
"What do they know about Asgardians?" Bruce said, trying to hide his disbelief but not quite succeeding.
"They're ex-SHIELD, so enough."
Bruce nodded reluctantly. "Call them. I'll clean him up, but I can't do much else."