The Gwaith-i-Mírdain (S. ‘People of the Jewel-smiths’; also called the Elven-smiths) were the Noldor of Eregion and the folk of Celebrimor (grandson of Fëanor). The height of their craft was the making of the Rings of Power.
The Noldor had settled Eregion around SA 750, in part due to its proximity to the mithril-mine of Khazad-dûm. The craftsmen of Eregion worked together with Durin’s Folk for nearly a thousand years; and it was at this time that the friendship and prosperity among the Elves and Dwarves were at their greatest.
At the ending of the First Age, they were the most skillful Elven craftsmen in all mortal lands, their skill being second only to Fëanor. The making of the Rings of Power was the greatest of their achievements, but also their downfall. When Sauron, disguised as Annatar, approached them around 1200, the Gwaith-i-Mirdain accepted his gifts and instruction. Under Sauron’s direction, nearly 1500 craftsmen forged the Rings of Power (though Celebrimor alone forged the Three Rings). Upon the completion of the Rings in 1590, Sauron betrayed the Noldor, forging the One Ring in secret. When Celebrimor discovered this, the Three Rings were hidden; but by now, Sauron had turned to open war. Eregion was overrun in 1697 and Celebrimor and most of the Gwaith-i-Mirdain slain.