Creator of Anglachel, Anguirel, galvorn
In that wood in ages past Melian walked in the twilight of Middle-earth when the trees were young, and enchantment lay upon it still. But now the trees of Nan Elmoth were the tallest and darkest in all Beleriand, and there the sun never came; and there Eöl dwelt, who was named the Dark Elf. Of old he was of the kin of Thingol, but he was restless and ill at ease in Doriath, and when the Girdle of Melian was set about the Forest of Region where he dwelt he fled thence to Nan Elmoth. There he lived in deep shadow, loving the night and the twilight under the stars.
(Silm, Chapter 16, Of Maeglin)
Then Beleg chose Anglachel; and that was a sword of great worth, and it was so named because it was made of iron that fell from heaven as a blazing star; it would cleave all earth-delved iron. One other sword only in Middle-earth was like to it. That sword does not enter into this tale, though it was made of the same ore by the same smith; and that smith was Eöl the Dark Elf, who took Aredhel Turgon's sister to wife. He gave Anglachel to Thingol as fee, which he begrudged, for leave to dwell in Nan Elmoth; but its mate Anguirel he kept, until it was stolen from him by Maeglin, his son.
(Silm, Chapter 21, Of Túrin Turambar)
He shunned the Noldor, holding them to blame for the return of Morgoth, to trouble the quiet of Beleriand; but for the Dwarves he had more liking than any other of the Elvenfolk of old. From him the Dwarves learned much of what passed in the lands of the Eldar.
Now the traffic of the Dwarves down from the Blue Mountains followed two roads across East Beleriand, and the northern way, going towards the Fords of Aros, passed nigh to Nan Elmoth; and there Eöl would meet the Naugrim and hold converse with them. And as their friendship grew he would at times go and dwell as guest in the deep mansions of Nogrod or Belegost There he learned much of metalwork, and came to great skill therein; and he devised a metal as hard as the steel of the Dwarves, but so malleable that he could make it thin and supple; and yet it remained resistant to all blades and darts. He named it galvorn, for it was black and shining like jet, and he was clad in it whenever he went abroad. But Eöl, though stooped by his smithwork, was no Dwarf, but a tall Elf of a high kin of the Teleri, noble though grim of face; and his eyes could see deep into shadows and dark places.