and thus [Huan] too came under the doom of woe set upon the Noldor, and it was decreed that he should meet death, but not until he encountered the mightiest wolf that would ever walk the world.
...
But when the wolf came for Beren, Felagund put forth all his power, and burst his bonds; and he wrestled with the werewolf, and slew it with his hands and teeth;
...
Therefore [Sauron] sent a wolf to the bridge. But Huan slew it silently. Still Sauron sent others one by one; and one by one Huan took them by the throat and slew them. Then Sauron sent Draugluin, a dread beast, old in evil lord and sire of the werewolves of Angband.
...
[Huan] turned aside therefore at Sauron's isle, as they ran northward again, and he took thence the ghastly wolf-hame of Draugluin, and the bat-fell of Thuringwethil.
...
Then Morgoth recalled the doom of Huan, and he chose one from among the whelps of the race of Draugluin; and he fed him with his own hand upon living flesh, and put his power upon him. Swiftly the wolf grew, until he could creep into no den, but lay huge and hungry before the feet of Morgoth.
...
There Beren slunk in wolf's form beneath his throne;
...
Lúthien was spent, and she had not time nor strength to quell the wolf. But Beren strode forth before her, and in his right hand he held aloft the Silmaril. Carcharoth halted, and for a moment was afraid. 'Get you gone, and fly!' cried Beren; 'for here is afire that shall consume you, and all evil things.' And he thrust the Silmaril before the eyes of the wolf.
...
In that moment Huan leaped from the thicket upon the back of the Wolf, and they fell together fighting bitterly; and no battle of wolf and hound has been like to it, for in the baying of Huan was heard the voice of the horns of Oromë and the wrath of the Valar, but in the howls of Carcharoth was the hate of Morgoth and malice crueller than teeth of steel;
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Silmarillion; Of Beren and Lúthien