This takes place after the Avengers, when Thor has brought Loki back to Asgard.
The word came out strangled and broken although there was nothing touching the bare skin of his neck. Loki closed his eyes as a noticeable shiver ran through him.
When his green eyes opened again the pain and sadness in them nearly cracked his brother's soul. Thor knelt beside the bars of Loki's cell, running his fingers over the icy metal, trying to look away but failing miserably. Loki's desperation drew him in.
"Loki, you must be punished for what you did," Thor said, but his words lacked conviction. "You killed many innocent humans."
"What are a few humans in the schemes and designs of gods?" Loki asked, a harsh laugh escaping his mouth and turning into a cough that echoed through the halls long after it had died down. He turned away from his brother, sitting with his back to the metal bars of his cage.
Thor shook his head. "Brother, I want to help you."
"You can't," Loki said, running his fingers through his tangled black hair. "If Odin has his way, I will die in this very spot."
"Or you could repent, and we could be brothers again." Loki's desperation had spread to Thor, who touched his brother's shoulder lightly. Loki pulled away abruptly and the movement brought on another coughing fit.
"I don't think I'll have time to repent, brother, even if I wanted to." He turned his head and Thor noticed for the first time the purple bruises under his eyes and his abnormally pale skin. As he looked at his brother, a drop of blood traced a path from the corner of Loki's mouth down his chin and dripped onto his pants.
"Loki, you're sick," Thor said, panic rising in his eyes and seeping through his voice.
"Yeah, I realized," Loki muttered, wiping his mouth with the sleeve of his shirt. "I get to die in a hole like an animal."
"I'll get a doctor." Thor stumbled to his feet, nearly tripping as he took a few steps away from the cell door. "Just stay there, I'll be right back." He ran down the hall, his calls for a doctor echoing back to Loki.
"Where am I going to go?" Loki asked out loud to the empty corridor, laughing quietly. The sudden silence was deafening and his façade of contempt and nonchalance faded away to be replaced by a quiet fear. He never thought he'd really die. All of his plans had been so carefully concocted, but he never factored in that he might simply get sick and die. He was a god and he was being defeated by something he couldn't even see. He coughed again and stared at the blood in his hand. This couldn't happen to him.
Fifteen minutes later, Thor came back. Alone. Loki raised his head at the sound of his brother's heavy footsteps.
"No one would come, would they?" he asked. There was a smudge of blood on his cheek and beads of sweat lined his forehead.
"No," Thor said, and he sounded like a wounded child. "Father said that if they did, he would have them executed."
Loki laughed. "Of course." He ran a shaking hand over his face. "Well, I guess this is goodbye then, brother."
"How can you say that, Loki?" Thor asked, gripping the bars of the cell until his knuckles turned white. "Maybe I could get you out of here, take you somewhere where they could help."
"And go down in history as the man who helped a murderer and a traitor?" Loki pulled himself to his feet so he was facing Thor. "You wouldn't do that for me. I'm not even your real brother."
"Family stretches beyond blood, Loki. You are my brother, in bond if not in blood, and I will not leave you here to die."
"Yes you will," Loki said, backing up slowly toward the metal cot on the back wall of the cell. "You will because if you don't, father will banish you again, for good this time. And father's high opinion of you has always been the most important thing in your life. Besides, what happened to 'you must be punished'?" He backed into the cot and sat down heavily on it. He leaned against the wall and closed his eyes. A small smile crossed his lips.
"It's good to hear you say you care, brother, even though I know it is a lie."
"It is no lie, Loki," Thor insisted as he watched the life fade from his brother. He had seen sickness before, but never one as rapid as this, that visibly sucked the life from a person. A thought flickered through Thor's mind; perhaps Odin had done this to Loki. Perhaps when Loki had arrived home in Asgard, Odin had discreetly introduced this fatal virus to his system. It would be a quick and efficient way to eliminate the threat that Loki posed to the future of Asgard.
Loki had opened his eyes slightly to watch Thor puzzle through his thoughts. When Thor looked at him, horrified, a smirk pulled up the corner of Loki's mouth.
"I'm assuming you've come to the same conclusion I have," Loki said, closing his eyes once more and lowering himself onto the cot so he was lying on his side. Some of his black hair fell over his face. "It was a good plan, I'll give him that." His voice disintegrated into a cough, shaking his whole body, expelling more blood onto the cold stone floor.
Thor watched desperately as his only brother died in front of his eyes. Only a simple row of bars kept him from saving his brother, his friend. Thor was about to drop to his knees hopelessly when he realized he still had one option. He held out his hand, summoning Mjolnir. The hammer tore through the brick walls of the dungeon easily and with one swing Thor had obliterated the bars of Loki's cell. He rushed in and lifted his brother off the cot, shaking his shoulders.
"Loki," Thor said quietly, tears gathering in his eyes. "I'm sorry, brother, I'm sorry. I did not mean for this to happen when I brought you home." Thor looked at Loki desperately, until the realization hit him that his brother was already dead. In the half of a minute that Thor had taken to summon his hammer, Loki had died quietly, leaving only a few drops of blood on the cold steel cot and a legacy of murder and anger.
Thor lowered Loki back on to the cot then knelt beside it, resting his head against the metal, its frosty touch burning his forehead and seeping into his brain.
"I'm so sorry. Brother."
Sorry that was so depressing. I just have a lot of Thor/Loki brother feels and I had to get some of them out. Please REVIEW and let me know what you thoughttttt!