Written for Back to Middle-earth Month 2011. This was originally part of "Hope For No Safety," but I thought that story worked better without it and decided to post this separately.
The waterfall and the cave are referencing a passage in HoMe explaining Elrond and Elros's names, though I haven't used the rest of that version.
Elwing stood alone, desperate and defiant. There was nowhere for her to go; she stood at the brink of the cliff, with only a long fall to the ocean behind her. The golden necklace she wore was finely wrought, set with countless lesser gems that reflected the light, but he cared nothing for its beauty and craftsmanship. Only the shining-bright Silmaril drew his eye, and he felt it resonate with the power of the Oath that bound him.
The waves splashed softly, far below. She still had not answered him. Maglor tore his gaze away from the jewel and raised his eyes to Elwing's face. Surely she must yield, he thought, in the next moment.
Elwing returned his look steadily, without sign of surrender. Suddenly she whirled, white garments streaming, and flung herself over the cliff's edge.
Dropping his sword, Maglor ran forward to catch her, but too late. He nearly followed her over the edge in his haste. His heart beat loudly in his ears, and he could not say for certain whether he heard the splash as the waves received her. Kneeling on the rough rock, he shielded his eyes with his hand and peered down into the darkness, although he knew no creature of earth could have survived such a fall. Nothing moved below, except for the foam of the tumbling waves and a single grey-white bird skimming westward across the water.
He slowly rose and turned away, sick at heart. He could not say himself whether his desperate grab had been to save her life, or the jewel; but both were lost. Elwing's words echoed in his mind: Where are my children, son of Fëanor?
The Silmaril was lost, carried away by Elwing's last mad act of defiance. His youngest brothers–- He should sing them a lament, but the weight of the Oath bore down on him, inexorable, choking his voice in his throat.
Where are my children, son of Fëanor?
Perhaps there was still something he could save.
He found them at last, in a rocky cave near the River Sirion half-screened by a small waterfall. Outside the cave, a dark-haired woman dressed in the style of the Sindar lay sprawled face-down on the riverbank. An arrow was lodged in her back; her bloodied clothing and her hair bore scattered droplets of spray from the waterfall like tiny jewels. Maglor knelt down beside her briefly, raising the body to look at her face. Not one he knew, though he would not have expected it. He could see she was not breathing, and he set her back down. She had done well, to come so far with such a wound.
Any others who had guarded them must be dead or fled; when he entered the cave, the boys were alone. They were curled up together as if asleep. His foot made a slight noise against a pebble, and they both lifted their heads.
Two pairs of grey eyes stared at him. "Mama?" one of them asked in a tentative voice.
You will never see her again this side of the Sundering Sea, child, because of me. Elwing had mortal blood; who could tell if she would even go to the Halls of Mandos as an Elf would?
It would do no good to frighten the children into running as their mother had. He did not have his eldest brother's height, but he must still seem very tall to them. He went towards them carefully and crouched down. There was nothing he could do about the blood on his armor and the smell of smoke in his hair. "I won't hurt you," he said inadequately.
They clung to each other as the twins, his brothers, had once done, their faces uncertain. He sang to them then, whatever came into his head, making his voice low and soothing like the sound of the waves. Eventually they drowsed, leaning against him. He wrapped them both in his red cloak and lifted them in his arms to carry them back.