Nuin is said to be very wise and loved to travel with his folk. Once he wandered far to the east of Palisor until curiosity led him to a strange place, with a mountainous wall. He found a passage which led to a valley inside a mountainous circle, Murmenalda, the Vale of Sleep. There he saw sleeping forms, others alone, other entangled into the arms of others. Frightened, he went back to Tu and told his tale, and Tu replied him that they were the Younger Children of Iluvatar.
The story, known as "Gilfanon's Tale", stops and its development is known only from outlines. According to them, Tu warned Nuin that it was not yet the time of Men to wake yet as they needed light, but Nuin visited the valley often and pondered on the figures. Accidentaly he stumbled against a sleeper who stirred, and then he was overcome with curiosity and awoke the first pair of Men, Ermon and Elmir, right before the first rising of the Sun from the West. Men were dumb and frightened, but Nuin taught them speech, some Ilkorin tongue, and thus was the Father of Speech. In another note, Nuin fights alongside Ermon in a fight against Fangli but he is killed by Goblins, a result of the betraying of Men.
Christopher Tolkien laments that "Gilfanon's Tale" remained unfinished and wondered whether his father consciously rejected the concepts of the story outright, or left it on hiatus, until his ideas were replaced by those of the later Silmarillion (Of Men).
- J.R.R. Tolkien, Christopher Tolkien (ed.), The Book of Lost Tales Part One, "X. Gilfanon's Tale: The Travail of the Noldoli and the Coming of Mankind"
- J.R.R. Tolkien, Christopher Tolkien (ed.), The Book of Lost Tales Part One, "X. Gilfanon's Tale: The Travail of the Noldoli and the Coming of Mankind": "Notes and Commentary"