Celegorm was the third son of Fëanor, born in Eldamar during the Years of the Trees. He came to be accounted among the followers of Oromë, and he learnt much of the lore of living creatures. While most of his brothers went to the house of Aulë when they were traveling near that area, Celegorm went rather to the house of Oromë. He had the best woodcraft of all the High Elves, and was known as the Huntsman of the Noldor. His closest friend and ally was Curufin.

Along with his father and brothers, Celegorm came to Middle-earth after swearing the Oath of Fëanor. They came to Lammoth, also known as the Great Echo, but soon travelled to Hithlum. There they made a camp by Lake Mithrim, and there Morgoth found them. There the Dagor-nuin-Giliath was fought. Celegorm stopped a group of Orcs with another group of Noldor from Eithel Sirion, and drove them into the Fen of Serech.

After that the Sons of Fëanor came to live east of Dorthonion. They protected that area from Morgoth, and Celegorm strengthened the Pass of Aglon along with his brother Curufin. This pass was an opening to Doriath. The brothers stayed there until the Dagor Bragollach.

After the destruction of his realm, Celegorm fell into evil patterns of thought. As neither he nor Curufin could do anything to fulfil their Oath at that time, their turned their counsel and arms,against their own kin.

They fled to Nargothrond and stayed with Finrod Felagund where they won great reknown. When Beren arrived, they were not pleased with his quest to find a Silmaril, for they believed that the Silmarils were theirs by right.

The two brothers came to dominate the counsels of Nargothrond, the city of Finrod Felagund. Eventually, they managed to force him to abdicate in favour of themselves.

One day Huan, Celegorm’s wolfhound, found Lúthien in the forest and took her to Celegorm. Celegorm told Lúthien that if she came with him back to Nargothrond, he would help her in any way he could. However, he then took her captive and led her to Nargothrond, in hopes that he could force Thingol into giving her hand to him.

Celegorm wished to become the greatest elf king that ever lived, and having Lúthien as a wife would help him greatly. But Huan felt that Lúthien’s captivity was not right, and he helped her escape.

Eventually the brothers were hounded out of Nargothrond for attempting to take over the throne, and they became outcasts, riding the plains with Huan at their side, for the dog had come back to Celegorm after helping Lúthien. They made their way toward their brother Maedhros’s home, and doing so, they came upon Beren and Lúthien. Celegorm tried to run over Beren in his anger, and Curufin lifted Lúthien off the ground into his saddle. Beren jumped out of the way and leaped onto Curufin’s horse. He took Curufin by the neck and pulled him off the horse and they wrestled on the ground. Celegorm came after him with a spear, but Huan jumped on his horse, because he had finally decided to betray his master. This deterred Celegorm, and Beren threw Curufin away from himself. The brothers then cursed Beren and Lúthien and made as to ride off, but Curufin then took Celegorm’s bow and shot it towards Lúthien twice. The first arrow Huan caught with his teeth, and the second Beren took, saving Lúthien from harm. From then onwards, Huan remained with Lúthien.

Later, after Thingol received a Silmaril from Beren, the Sons of Fëanor were angry. They asked Thingol to give the jewel to them because of their oath, but he refused. Many years later it was heard among Celegorm’s kin that a Silmaril was seen in Doriath again, around the neck of Dior Eluchíl, Thingol’s heir.

The Silmaril was then fastened in the great necklace of the Nauglamir. The sons sent a claim to Dior Eluchíl, telling him about their oath, and when Dior Eluchíl did not answer, Celegorm roused his brothers and decided to assail Doriath. They came upon Dior Eluchíl in the middle of winter in Menegroth, and there the second slaying of Elf against Elf occurred.

Dior Eluchíl killed Celegorm and in that assault Curufin and Caranthir were also slain. Dior Eluchíl also fell, but the sons of Fëanor still did not gain the Silmaril as the remnants of Dior Eluchíl’s folk took it with them and ran off.

In the notes for a planned “excursus” on the names of the Sons of Fëanor (c.1968) Tolkien gave his Quenya name as Turkafinwë ‘strong, powerful’ (physically) In these same notes his mother-name is given as Tyelkormo ‘hasty riser’ thought to be from his readiness to leap to his feet when enraged. (Source: HoME Vol.XII, The Shibboleth of Fëanor)