Disclaimer: This was originally a one-shot, but at the pleading of several reviewers, I've decided to acquiesce to their wishes and write more. I own nothing but the idea which formed the story, and I make no profit from having written it. Characters within belong to Marvel. Summary (I believe) written by kaedith on Tumblr.
Thor scanned the walls of the forgotten place and found more words awaiting him there. Some, like the ones scrawled on the floor, were written in blood, once red and long since gone black. Others were merely imprinted through the grime and partially erased by time. Angry words, sorrowful words. Words swearing revenge, and words begging forgiveness. He stepped through the room slowly, reading the words written by the forsaken once Prince and he stopped at one wall. This wall seemed at first no different from the others, words scrawled across it begging forgiveness and promising pain if he ever escaped.
Thor knelt down, crouching carefully in the dirt and looked at the words written at the bottom of the wall, scraped in over and over and smeared in blood both old and new. 'I am Loki', it said. One sentence over and over, written straight across the bottom of that wall. As if Loki had written it to remind himself of his name, of his existence.
He straightened up again and turned, walking with slow, sure steps toward the opposite corner. In this corner, Loki was curled. He lay in the dirt, in the filth and the grime. It coated his body thickly so he almost blended into the place which had been his prison for so long. His hair was impossibly tangled into dark dreadlocks as dirty as the rest of him, lying long about his naked and filthy form like the legs of a hungry spider.
Thor stopped when he stood over this sad creature, the one who had brought upon Asgard destruction and ruin. There was nothing to Loki's figure, so thin and neglected, that was like the arrogant Trickster who had stood before the shining city and ordered his minions to bring about its downfall so long before. Asgard had won that day, but only barely. Ragnarok had been averted, but only just, and Loki had been found, captured and then thrown into this foul pit to rot.
And now, a century later when Thor finally had leave to come to Loki, take the chance to ask him why, ask him what had driven him to his act of ultimate betrayal, he wondered if the answer mattered any more. Here was the one who had been his brother, and was his brother still. The Frost Giant who wore an Aesir skin, who was called monster, and who had betrayed. But perhaps it was Loki who had been betrayed first. Maybe the answer mattered after all, for how else would Thor know how to prevent it a second time?
"Loki." He spoke, his voice soft but piercing in the otherwise silence.
Loki jerked and turned, eyes wide in surprise. He had taken no note of Thor's soft footfalls, perhaps in his long isolation he had forgotten what footsteps sounded like. Thor stared into those green eyes, wide with terror but dull with magic long chained by the collar around his neck. Once it had been polished gold, but now it was as dirty as the rest of him. Those eyes were like a deer's eyes, Thor thought. The eyes of cornered prey. Eyes Loki was never meant to have.
Slowly the terror faded from those eyes, to be replaced by an emotion Thor didn't understand, for he had never seen bleak despair before and so could not recognize it. "One and one and one again." Loki spoke softly, his voice slurred and clumsy, his once quick and clever tongue slow and sluggish from disuse. "One and one and one. You have come. You are here." He turned slowly in the grime and sat up, keeping his eyes on Thor's the entire time he moved.
"I am here." Thor answered him, though he was uncertain what Loki meant.
Loki glanced at Mjölnir, then back at Thor and a strange hope began to bloom in his eyes. "It is time?"
Thor frowned slightly in puzzlement. "Loki, I have come for you."
"Yes." Loki sighed and his eyes closed briefly before he opened them once more. He began to smile and tears escaped his eyes to work their stubborn way down his cheeks, creating furrows in the dirt. "Loki. I am Loki. You are so kind to say it. So kind." He shifted into a kneel before Thor and bowed his head.
It was several moments before Thor realized what Loki was doing, and that realization struck him to his very core. He was sitting such as a condemned man would sit before his executioner. Loki thought that Thor had come to kill him.
Thor reached down to grasp a filthy arm and pull Loki all unresisting, to his feet. "No, brother." He said, pain in his eyes and voice. "I haven't come to kill you. I've come to take you home."
The confusion in Loki's eyes quite nearly broke Thor's heart and then he looked at the hand grasping his arm. "Brother...?" He intoned softly. His head snapped back up, expression an open mask of shocked surprise. "You are Thor."
Thor's heart did break then. It had been so long that Loki had forgotten what Thor looked like. Caring not for the grime that coated Loki's body, Thor pulled him close in an embrace. "It's time to go home, brother." He spoke softly. "I'm here to take you home."
"Home..." Loki closed his eyes and leaned against Thor. He allowed himself to be led out into the light, allowed himself to be taken back to Asgard.
It was not only Loki's words that had come a hundred years too late, but so had Thor's. Loki's penance was over, but for Thor it was only just beginning.