Over the course of The Silmarillion, Celegorm--the third son of Fëanor--evolves from a loyal follower of Oromë to one of the most nefarious of the Eldar. Typically considered by fans to be appropriately classed as one of the bad-boy Fëanorians among the "three Cs", the evolution and final presentation of the character of Celegorm nonetheless conveys a character of complex motivations who possesses perhaps the most diverse talents of any of the sons of Fëanor.
Celegorm is called "the fair" in The Silmarillion, an epithet that appeared early in the development in his character and made it through to the published version. While early evidence suggests that Tolkien intended Celegorm to have golden "gleaming hair" (HoMe 3, Lay of Leithian, Canto VI and the translations of names into Old English given in HoMe 4), whether this was meant to survive into the published version is subject of fan debate. More certainty can be given to Celegorm's personality and skills. His Quenya name Turkafinwë Tyelkormo given in The Shibboleth of Fëanor (HoMe 12) indicates that he was strong in body and hasty in his temper. According to The Silmarillion, he was an avid hunter as far back as his days in Valinor, where he followed Oromë and often went to his house.
From his love of nature, the idea was derived that Celegorm also knew how to speak all of the languages of the birds and beasts on earth. Indeed, Celegorm more so than any of the brothers seems to possess his father's gift not only for languages but for persuasive speaking. Twice in The Silmarillion, the passionate words of Celegorm rouse his audience to (not entirely wise) action. And so from the outset of The Silmarillion--before the Noldor have left Valinor even--we are given a character with a strong physical presence, a unique attachment to one of the Valar, and gift for speech akin to that of Fëanor.
Upon arriving in Beleriand, Celegorm alone of the sons of Fëanor is mentioned for special prowess in the Battle-under-stars where he destroyed a large contingent of Morgoth's army. Celegorm's role in the story diminishes for a time after that, making way for the political maneuverings of his eldest brother Maedhros. Along with the other sons of Fëanor, after Maedhros forgoes the crown to Fingolfin, Celegorm resides in eastern Beleriand. In Himlad, he lives with his brother Curufin, and together, they hold this realm until the Battle of Sudden Flame drives them to seek haven in Nargothrond.
Celegorm is mentioned specially also as the friend of Aredhel, and it was Celegorm whom she sought after leaving Gondolin. The two characters are portrayed throughout the drafts and into the published Silmarillion as having a close friendship, and in the Maeglin section of Volume 11, Celegorm aids Aredhel and Maeglin in their escape from Eöl by lending horses and attempting to waylay Eöl when he attempts to cross Himlad.
Doubtlessly, however, Celegorm's most prominent role in the history of the Noldor concerns his deeds in Nargothrond. Following the Battle of Sudden Flame, he fled to Nargothrond with Curufin, and they were welcomed by their cousin Finrod and quickly gained a powerful following. When Finrod sought to keep his oath to Barahir by aiding Beren in recovering a Silmaril, it was Celegorm whose impassioned speech convinced all but ten of the people of Nargothrond to forsake their king. Here, the words of Celegorm were "as potent as were long before in Tirion the words of his father that first inflamed the Noldor to rebellion" ("Of Beren and Lúthien"). Here also begins the machinations of Celegorm and Curufin to send Finrod to his death, take over Nargothrond--the largest realm in Beleriand--and gather power once more to the House of Fëanor.
After Finrod left Nargothrond, Celegorm's hound Huan found Lúthien fleeing along the borders of Doriath and returned her to her master. Thinking she had found allies in the Noldorin princes, she cast aside her enchanted cloak, and Celegorm fell in love with her. With Curufin, he brought her back to Nargothrond and held her captive, intending to force her into marriage to also gain power in Doriath. However, Huan betrayed his master and aided Lúthien's escape, and learning the truth of Celegorm and Curufin's deeds, the people of Nargothrond at last cast them out of the kingdom and gave their loyalty to Finrod's brother Orodreth.
Celegorm and Curufin, intending to return to Maedhros in the east, encountered Beren and Lúthien on the way, and Beren attempted to kill Curufin after Curufin's thwarted abduction of Lúthien, it was Celegorm who saved his brother's life. Huan, however, impeded Celegorm from killing Beren, and the hound at last turned on his master.
From this, Celegorm and Curufin developed a strong hatred of Thingol and Doriath, vowing to kill anyone from that realm whom they found. When word arrived that Dior of Doriath kept a Silmaril, it was Celegorm's impassioned words that drove his brothers to launch the second kinslaying against Doriath. Here, Celegorm managed to kill Dior but died from the wounds that Dior inflicted upon him, the follower of Oromë and lover of the natural world forgotten in lieu of a traitor and a kinslayer.
Celegorm's role in the events in Nargothrond underwent a peculiar evolution as J.R.R. Tolkien developed The Silmarillion over the course of his life. In the A-text of The Lay of Leithian, Celegorm played the role that would later be given to Finrod Felagund. It was Celegorm who was rescued by Barahir at the Battle of Sudden Flame, and Celegorm who swore an oath to him (in addition to the Oath of the Fëanorians) and gave Barahir a ring as a sign of his promise. The ring is identical to the Ring of Barahir that appears in The Silmarillion and The Lord of the Rings: two serpents entwined. Only now, it was identified as being made by Fëanor and as a crest that belonged to his house.
Following his oath to Barahir, Celegorm with Curufin founded Nargothrond, and so it was to Celegorm that Beren made his plea for aid. The conflict of two disparate oaths now belongs to one man--versus two powerful characters with conflicting motives--and Celegorm chooses his oath to Barahir when Beren arrives, requesting aid. He gives Beren Noldorin guides and also a magic knife that he will use to cut the Silmaril from Morgoth's crown.
When Felagund later took this role, the story began to evolve into the more sinister published version. Celegorm's motivations slowly changed: At first, he captured Lúthien for love of her and returned her cloak to her, though he refused her further aid. Later, of course--influenced by Curufin--he had political motivations in desiring marriage with her as well and Huan took his role in facilitating her escape. The "magic knife" used to cut the Silmaril from Morgoth's crown is not given by Celegorm but taken from Curufin as punishment for his foul treatment of Lúthien. And so we come to the story as it is published in The Silmarillion, where Celegorm and Curufin have evolved from complex characters with complex motives into villains.
