Caranthir (S. ‘Red–‘) was the fourth son of Fëanor. Of the Sons of Fëanor, he was most quick to anger. In Middle-earth, he settled in Thargelion and grew rich from trade with the Dwarves of Ered Luin. When Thargelion was overrun by Orcs during the Dagor Bragollach, Caranthir fled south to join Amrod and Amras.
He later recruited the services of the treacherous sons of Ulfang and fought with them during the Nirnaeth Arnoediad–but unbeknownst to him at the time, the sons of Ulfang were secretly in alliance with Morgoth. At the height of battle, they betrayed Caranthir and brought ruin upon the whole Eldarin army. Wounded, Caranthir returned with his brothers Celegorm and Curufin to Beleriand, still seeking ways to fulfill their Oath. The more they wandered, the more evil their thoughts and actions became.
When they heard that a Silmaril had been recovered from Morgoth’s Iron Crown, they hid in Menegroth. They attacked Dior, the new ruler of Menegroth, but the Silmaril had already been passed to Dior’s daughter, Elwing; and while the three brothers killed the Heir of Thingol and destroyed Doriath, they were themselves slain.