Orcs: History (p2)

Melkor was the first to learn of the Awakening of the Elves. He soon began sending evil spirits among the Elves, who planted seeds of doubt against the Valar. It is also rumoured that some of the elves were being captured by a "Rider" (Oromë) if they strayed too far, and the elves later believed these lies were brought to Utumno, where they were cruelly tortured and twisted into Orcs.