A/N: This isn't the fic- this is more like a history (hence the title "A History"). The real story shall come in due time.
Disclaimer: I own Mirnim. Mirnim is my brainchild! Everything else belongs to Tolkien.
Mirnim's History
She was once come from that of great lineage. Greater than the Kings of Gondor, or the Elves of Mirkwood; she was far greater than any that roamed Middle-Earth. Indeed, she was elder than any of the races of Arda, but not the Eldest. She was the youngest of the Great, the Valar that created Valinor and shaped the Great Lamps and the Great Trees that gave light. She was the one who gave light to both the Trees and the Lamps, but they were both taken by a ruthless spirit, exiled by the Valar.
His name was Melkor, or as the peoples of Middle-Earth would call him, Morgoth. He was ruthless in both mind and body, as he envied the Valar, and especially the King of the Valar. He hated Manwë and Varda, Lady of the stars, simply because he wanted their power. He fought with the both of them, and all the other Valar, in many wars, and Melkor destroyed many of their creations, which they had to rebuild. Their biggest losses were the Great Lamps and the Great Trees, which they never rebuilt. Fortunately, they were able to keep their greatest possession, or at least, keep her alive.
She was conceived after the destruction of the Trees, though half of her light was given to the Lamps and the Trees. This is why she was born young and naïve, though she was destined to become great. She was named Mirnim in the language of the Elves, for the white jewel that glowed inside her gave light to the world. She was hidden from Melkor for decades, for fear off abduction; the Valar were smart enough not to put it past Melkor to commit something like this.
The day they let Mirnim set foot onto Middle-Earth was a day to regret. Melkor kept his fortress under cover of darkness beneath the earth, and has kept many minions in his service on the surface. She settled herself in Valinor and gazed upon the First Born, or Elves. She frolicked with the creatures carelessly, with her parents thinking that she was safe in the world, though that she was far from. She was growing, but she was young, and still naïve for her age. A fair figure of a man came to her, but he merely talked to her. He charmed her into submission, and seduced her to the point of no return, and he took her, planting his seed of malice in her. Then her presence was lost to the Valar.
He revealed himself as the one and only Melkor, the banished one, and by the time the Valar found out about his malevolence, it was too late for them to achieve anything to save her. And so her light was stolen from her, and she was no longer called Mirnim, but Wethril, the shadowy one. He kept her as his own, and convinced her that she was destined for greatness. Little did he know that there was still light left in her being, something that she knew in her heart. This little aspect would factor in the defeat of all malevolent spirits.
Over the years, she accompanied Melkor with his evil schemes to corrupt and control the world, but each and every time, she would find a way to thwart his mind. She was always punished, but she was immortal, so her wounds healed fast, as all of the Valar are said to have done. Day by day, with notice from neither Melkor nor Wethril, Mirnim's light began to grow like the mallorn trees of Lothlorien. But no longer would they grow, for she was taken to Sauron, the Dark Lord, and her light was once again taken from her to make the One Ring. Again, she was taken over to the dark side.
She fought in many wars, for and against the side of good. She was always standing at a crossroad between both sides, for many of those wars were with the Valar spirits, and no harm would come to either of them. In confusion, she ran away out of sight of Melkor and Sauron, abandoning the name Wethril. The name Mirnim was lost to her; she had neither memory of it nor any reference to it, as her light was almost out. Her memory of her past was wiped clean.
The middle of the Second Age came, and the Earth was in turmoil. The Three Rings were hidden after a war with the Elves and Sauron, and then the Last Alliance was forged. The nameless warrior, as she called herself for she had no name, merely stood by and watched as the two armies clashed. Seeing Sauron again unearthed deep, dark memories that nearly consumed her from the inside. But seeing how the Elves and Men fought and died for the safety of Middle-Earth inspired her to do something she would have never thought of achieving. She picked up a single arrow and bow, and waited for Sauron's descent. When it seemed that he was the victor over the armies after he had slain the King, She took up the arrow and drove it into his chest, giving Isildur the chance to defeat Sauron once and for all. None, save Elrond, witnessed her presence upon the mountain.
The defeat of Sauron was only the start of her recovery, but it was only a slow start, for Isildur's heart was not ready to give up the Ring. She could feel the urge inside of her for Elrond, not Isildur, to destroy the Ring, but his repudiation made her heart bleed. When the King was slain, the Ring was lost, and so was she. The Nine had been unleashed once more after Sauron's defeat, and she could sense this in her heart. By chance, she happened to encounter one, and received the Black Breath, that had her paralyzed. After that, she saw no more, and her memory was wiped out once again.