Durin I was the eldest of the seven Fathers of the Dwarves, the first of that race to be created by the Vala Aulë. He was set to sleep under the mountains of Middle-earth until after the awakening of the Elves.
When he woke, he journeyed in the wilds until he came upon the Mirrormere, the lake that the Dwarves call Kheled-zâram. Looking upon mysterious stars reflected in its surface, he took this as a sign, and there founded a great city tunnelled in the heart of the Misty Mountains. This was Khazad-dûm, later called Moria.
Durin lived to a great age even by the measure of the Dwarves, but though he was called the Deathless, he was not immortal. He died some time before the end of the First Age, but he founded the line of the Kings of Durin's folk that extended down through the history of Middle-earth.