His name meant 'great dog', or 'hound'.

Huan was a wolfhound given to Celegorm by Oromë in Valinor. He followed Celegorm into exile, and thus came under the Doom of the Noldor.

It was decreed that he would die, but not before he encountered the world's mightiest wolf. He would also talk three times before his death, although he could understand any speech. Nothing could escape his sight or scent, and he never slept. No enchantments could overpower him.

He first met Lúthien when out hunting with Celegorm. When Celegorm imprisoned her, Huan became her ally and helped her to escape. He then spoke for the first time, giving her counsel.

Together they fled north to save Beren, with Huan letting Lúthien ride on his back. At the bridge of Sauron's fortress, Huan slew all the wolves that were sent to kill them. He fatally wounded the werewolf called Drauglin who ran back to Sauron and died at his feet, but not before telling Sauron that Huan was near. Then Sauron took the shape of a wolf and battled with Huan. Huan triumphed, and after changing his shape many times, Sauron had to give up his body entirely.

Huan then went back to Celegorm, but when Celegorm tried to harm Beren and Lúthien, Huan attacked him, and saved his friends. He caught an arrow in his mouth when Celegorm tried to shoot Lúthien, chased Celegorm and Curufin to get them away, and then brought back herbs to heal Beren's wounds.

He once took the form of Draugluin to help Lúthien find Beren. After re-uniting them, he spoke for the second time, saying that he could go no further with them then, but they would meet again.

He then went on the Hunt for Carcharoth with Beren and Thingol. He slew Carcharoth, but was mortally wounded himself in the fight. He then spoke for the third time, saying farewell to Beren. He was carried back on a bier next to Beren's side.