§ Of the Coming of the Elves and the Captivity of Melkor The Silmarillion

Yet many of the Quendi were filled with dread at his coming; and this was the doing of Melkor. For by after-knowledge the wise declare that Melkor, ever watchful, was first aware of the awakening of the Quendi, and sent shadows and evil spirits to spy upon them and waylay them. So it came to pass, some years ere the coming of Oromë, that if any of the Elves strayed far abroad, alone or few together, they would often vanish, and never return; and the Quendi said that the Hunter had caught them, and they were afraid. And indeed the most ancient songs of the Elves, of which echoes are remembered still in the West, tell of the shadow-shapes that walked in the hills above Cuiviénen, or would pass suddenly over the stars; and of the dark Rider upon his wild horse that pursued those that wandered to take them and devour them. Now Melkor greatly hated and feared the riding of Oromë, and either he sent indeed his dark servants as riders, or he set lying whispers abroad, for the purpose that the Quendi should shun Oromë, if ever they should meet.