From The Book of Lost Tales 2: “The Fall of Gondolin” (1917) (pp. 151-2)
Now the folk whence Tuor came wandered the forests and fells and knew not and sang not of the sea; but Tuor dwelt not with them, and lived alone about that lake called Mithrim, now hunting in its woods, now making music beside its shores on his rugged harp of wood and the sinews of bears. Now many hearing of the power of his rough songs came from near and far to hearken to his harping, but Tuor left his singing and departed to lonely places. Here he learnt many strange things and got knowledge of the wandering Noldoli, who taught him much of their speech and lore; but he was not fated to dwell for ever in those woods.
Thereafter ‘tis said that magic and destiny led him on a day to a cavernous opening down which a hidden river flowed from Mithrim. And Tuor entered that cavern seeking to learn its secret, but the waters of Mithrim drove him forward into the heart of the rock and he might not win back into the light. And this, ‘tis said, was the will of Ulmo Lord of Waters at whose prompting the Noldoli had made that hidden way.
From The Shaping of Middle-earth, Part III “The Quenta”, 16, (c. 1926) (pp. 168 ff.)
Now Húrin of Hithlum had a brother Huor. The son of Huor was Tuor. Rian Huor’s wife sought her husband among the slain upon the field of Unnumbered Tears, and there bewailed him, ere she died. Her son was but a child, and remaining in Hithlum fell into the hands of the faithless Men whom Morgoth drove into that land after the battle; and he became a thrall. Growing of age, and he was fair of face and great of stature, and despite his grievous life valiant and wise, he escaped into the woods, and he became an outlaw and a solitary, living alone and communing with none save rarely wandering and hidden Elves.
Of a time Ulmo contrived, as is told in the Tale of the Fall of Gondolin, that he should be led to a river-course that flowed underground . . .
It has been told that Huor the brother of Húrin was slain in the Battle of Unnumbered Tears; and in the winter of that year Rían his wife bore a child in the wilds of Mithrim, and he was named Tuor, and was taken to foster by Annael of the Grey-elves, who yet lived in those hills.
Now when Tuor was sixteen years old the Elves were minded to leave the caves of Androth where they dwelt, and to make their way secretly to the Havens of Sirion in the distant south; but they were assailed by Orcs and Easterlings before they made good their escape, and Tuor was taken captive and enslaved by Lorgan, chief of the Easterlings of Hithlum. For three years he endured that thraldom, but at the end of that time he escaped; and returning to the caves of Androth he dwelt there alone, and did such great hurt to the Easterlings that Lorgan set a price upon his head.
But when Tuor had lived thus in solitude as an outlaw for four years, Ulmo set it in his heart to depart from the land of his fathers, for he had chosen Tuor as the instrument of his designs; and leaving once more the caves of Androth he went westwards across Dor-lómin, and found Annon-in-Gelydh, the Gate of the Noldor, which the people of Turgon built when they dwelt in Nevrast long years before.
From Unfinished Tales, Part One, I “Of Tuor and his Coming to Gondolin” (pp. 17 ff.)
Morgoth broke his pledges to the Easterlings that had served him, and he denied to them the rich lands of Beleriand which they had coveted, and he drove away these evil folk into Hithlum, and there commanded them to dwell. And though they loved Morgoth no longer, they served him still in fear, and hated all the Elven-folk; and they despised the remnant of the House of Hador (the aged and women and children, for the most part), and they oppressed them, and wedded their women by force, and took their lands and goods, and enslaved their children. Orcs came and went about the land as they would, pursuing the lingering Elves into the fastnesses of the mountains, and taking many captive to the mines of Angband to labour as the thralls of Morgoth.
Therefore Annael led his small people to the caves of Androth, and there they lived a hard and wary life, until Tuor was sixteen years of age and was become strong and able to wield arms, the axe and bow of the Grey-elves; and his heart grew hot within him at the tale of the griefs of his people, and he wished to go forth and avenge them on the Orcs and Easterlings. But Annael forbade this.
...[Annael tells Tuor to come with him and his folk to the south where the Elves still live free; though Tuor expresses an interest in finding Gondolin and fighting with King Turgon against Morgoth.]
Thus it came to pass that the Elves forsook the caves of Androth, and Tuor went with them. But their enemies kept watch upon their dwellings, and were soon aware of their march; and they had not gone far from the hills into the plain before they were assailed by a great force of Orcs and Easterlings, and they were scattered far and wide, fleeing into the gathering night. But Tuor's heart was kindled with the fire of battle, and he would not flee, but boy as he was he wielded the axe as his father before him, and for long he stood his ground and slew many that assailed him; but at the last he was overwhelmed and taken captive and led before Lorgan the Easterling. Now this Lorgan was held the chieftain of the Easterlings and claimed to rule all Dor-1ómin as a fief under Morgoth; and he took Tuor to be his slave. Hard and bitter then was his life; for it pleased Lorgan to treat Tuor the more evilly as he was of the kin of the former lords, and he sought to break, if he could, the pride of the House of Hador. But Tuor saw wisdom, and endured all pains and taunts with watchful patience; so that in time his lot was somewhat lightened, and at the least be was not starved, as were many of Lorgan's unhappy thralls. For he was strong and skilful, and Lorgan fed his beasts of burden well, while they were young and could work.
But after three years of thraldom Tuor saw at last a chance of escape. He was come now almost to his full stature, taller and swifter than any of the Easterlings; and being sent with other thralls on an errand of labour into the woods he turned suddenly on the guards and slew them with an axe, and fled into the hills. The Easterlings hunted him with dogs, but without avail; for wellnigh all the hounds of Lorgan were his friends, and if they came up with him they would fawn upon him, and then run homeward at his command.
Thus he came back at last to the caves of Androth and dwelt there alone. And for four years he was an outlaw in the land of his fathers, grim and solitary; and his name was feared, for he went often abroad, and slew many of the Easterlings that he came upon. Then they set a great price upon his head; but they did not dare to come to his hiding-place, even with strength of men, for they feared the Elven-folk, and shunned the caves where they had dwelt. Yet it is said that Tuor's journeys were not made for the purpose of vengeance; rather he sought ever for the Gate of the Noldor, of which Annael had spoken.
But he found it not, for he knew not where to look, and such a few of the Elves as lingered still in the mountains had not heard of it.
Now Tuor knew that, though fortune still favoured him, yet in the end the days of an outlaw are numbered, and are ever few and without hope. Nor was he willing to live thus for ever a wild man in the houseless hills, and his heart urged him ever to great deeds.
...[A spring of water, a sign from Ulmo, leads Tuor to the Gate of the Noldor and the beginning of his adventure.]