He became involved with the Quest for the Silmaril when Beren and Lúthien had to pass him on their way in. Lúthien enchanted him with her magic, but on their way out Carcharoth attacked before Lúthien could enthrall him again. Beren held out the captured Silmaril in an attempt to stay the beast, but Carcharoth bit off Beren's hand at the wrist with Silmaril and all.
The Silmaril burnt away Carcharoth's insides, and he became crazed with pain. A terror to Eldar, Men and Orcs alike, he passed south through Beleriand, until he arrived in Doriath. There Beren Erchamion, Elu Thingol, Beleg Cúthalion and Mablung joined with Huan the Hound to Hunt the Wolf.
Carcharoth was killed by Beren and Huan, but both Beren and Huan were slain. When Mablung cut open the belly of the beast, he found there the Silmaril with Beren's hand still around it, but when he touched the flesh it was swept away by a wind.
The story of Beren losing his hand to Carcharoth was modelled after the Germanic legend of the god Tyr, who lost his hand to the wolf Fenris.