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.
- Upon the threshold, watchful, dire,
- his eyes new-kindled with dull ifre,
- towered Carcharoth, a biding doom:
- his jaws were gaping like a tomb,
- his teeth were bare, his tongue aflame;
- aroused he watched that no one came,
- no flitting shade nor hunted shape,
- seeking from Angband to escape.
- Now past that guard what guile or might
- could thrust from death into the light?
- He heard afar their hurrying feet,
- he snuffed an odour strange and sweet;
- he smelled their coming long before
- they marked the waiting threat at door.
- His limbs he stretched and shook off sleep,
- then stood at gaze. With sudden leap
- upon them as they sped he sprang,
- and his howling in the arches rang.
- Too swift for thought his onset came,
- too swift for any spell to tame;
- and Beren desperate then aside
- thrust Lúthien, and forth did stride
- unarmed, defenceless to defend
- Tinúviel until the end.
- With left he caught at hairy throat
- with right hand at the eyes he smote -
- his right, from which the raidance welled
- of the holy Silmaril he held.
- As gleam of swords in fire there flashed
- the fangs of Carcharoth, and crashed
- together like a trap, that tore
- the hand about the wrist, and shore
- through brittle bone and sinew nesh,
- devouring the frail mortal flesh;
- and in that cruel mouth unclean
- engulfed the jewel's holy sheen.
- The final paragraphs of the Lay of Leithian.
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 perhaps modelled after the Germanic legend of the god Tyr, who lost his hand to the wolf Fenris.