Also called 'the Black'. His name meant 'Rushing jaws'.

Ancalagon was the greatest of Morgoth's dragon host, and he was first heard of in the War of Wrath where he led the dragon host. However, he was slain by Eärendil with the help of the eagles.

When he fell from the sky, he landed on the towers of Thangorodrim, Morgoth's fortress, and crushed the towers in his death throes.
Encyclopedia entry originally written by Hathaldir