The Silmarillion, HoME, and the Book of Unfinished Tales belong to JRR Tolkien. I am not JRR Tolkien. Therefore, anything you recognize from those sources belongs to him, and not to me.
Maedhros hadn't been sure what to expect from death. He'd assumed he'd either find Namo glaring down his nose at him, or that the 'everlasting darkness' would turn out to be an end to his existence. He'd been hoping for the latter, in all honesty.
Instead, there was light, and lots of it. Nothing but light. Then a still, small, voice that didn't need to be loud to have his entire attention.
"Nelyafinwe Maitimo Maedhros Russandol," it said.
"Yes, my Lord?" said Maedhros. It was probably Lord Namo, and being polite couldn't hurt.
"Nay, child, I am not one of your Valar. I am Eru. You are in the Timeless Halls," Eru said.
"Oh," said Maedhros, feeling very small. Why was this happening to him, of all people? After everything he'd done. Eru was surely furious with him, if he cared about him at all.
"Do you regret taking the Oath of Feanor, and your actions in its pursuit?" asked Eru.
"Yes," said Maedhros quietly. The whole business had been hopeless from the start, and had brought his family nothing but ruin. Even the Silmarils had rejected them in the end.
"Then you have a choice. You can cease to exist, as you were hoping when I brought you here. You can report to Namo for judgement. Or, you can go back and do things differently this time round."
"I don't understand," said Maedhros. "How is that possible? Once part of the music has been played, surely it cannot be played again. Beyond that, I have always been told our fates are set out in the music before we are ever born."
"You are familiar with the musical term DS al fine?" asked Eru.
"I have Maglor as a brother," snapped Maedhros. "It means go back to the sign, and from then to the end." From then to the end?
"Exactly," said Eru. "The music has a potential repeat with second ending here. What would you do differently, if you could?"
"Not swear that – The Oath," said Maedhros. "Not rely on Caranthir's judgement of Ulfang and his sons. Not kill any elf over the Silmarils. Not trust Father to go back for Fingon and Fingolfin, or to behave rationally after he loses Grandfather and the Silmarils. Not attempt to treat with Morgoth to retrieve a Silmaril, then get my people killed, and myself captured for use as a hostage. Try to talk Maglor and Pityo at least out of taking the Oath."
"Do you want to do this, then?" asked Eru.
Maedhros hesitated. Would he be strong enough to resist his father's madness on that terrible night? Could he endure all that grief and pain over again, knowing what was to happen? The darkness seemed to beckon. It would be easier. But when had he ever refused to undertake a task because it was hard? This was his mess to right, if he could.
"Why are you offering me this?"
"Because I am not fully in agreement with the Valar's actions – though that does NOT mean I support yours, or Feanor's, let alone Melkor's. Know this: I never held you to your Oath. I would rather that you had broken it, than that you allowed yourself to become a mass murderer in an attempt to fulfill an Oath you should never have sworn." Eru let that sink in for a few moments.
If Maedhros could have wept, he would. It had really been so easy? All he'd needed was trust? "Why didn't you tell me?" he screamed. "I wanted to stop, but I was too damn scared I'd doom my entire family to eternal darkness if I gave up on that bloody Oath! Why didn't someone tell me?"
"Maglor tried to tell you. You knew in your heart that he was right. You let your fears drive you into evil and madness, until you slew yourself in despair."
Maedhros floated silent in the light. "But…" he began slowly. "Surely someone was holding us to it? I could feel it tugging at my mind, whispering in my heart. Did Manwe and Varda…"
"None of you asked them for release. Yet Namo has not cast your father or your brothers into the eternal darkness. Your dead kin are in Mandos."
"Then whose was the voice?" asked Maedhros.
"Can you not recognize Morgoth's voice, you who suffered so much at his hands?"
Maedhros' mind ground to a halt. He had been manipulated by the one against whom he had taken the Oath in the first place? Maedhros discovered that hysterical sobs were entirely possible after all. After an unknown time, though surely that was meaningless in the Timeless Halls, he calmed, though he still felt both sad and terribly empty.
The voice spoke up again. "I am also doing this because I love you. I know you regret your actions that harmed so many of my children, yourself not least among them. I do not like to see any child of mine destroy himself."
"How can you love me? I've become a monster as bad as the orcs." said Maedhros.
"I love you, and I always will."
"I don't understand."
"You do not have to. Only know that it is so. Will you go, and undo the evil you have done?"
"I will go, my Lord," said Maedhros. "And I will try with all I am to make things better this time."
"Just do your best," said Eru, "and my blessings will go with you."
"Thank you," Maedhros whispered.
A/N 2: Yes, this is a 'go back in time to before the Darkening to attempt to fix things' story that stars a son of Feanor whose name begins with M. It will be longer than most of my stories. Beyond that, it should be pretty different from Kenobi Skywalkers' Duplicity. That's an interesting story, by the way. I hope they continue it.