Ancalagon
Ancalagon, also known as Ancalagon the Black, was the greatest of all winged dragons. He was bred by Morgoth during the First Age and was the largest dragon to have ever existed in Middle-earth. His appearance in history was restricted to the War of Wrath.
After Eärendil made his journey to Valinor to convince the Valar to overthrow Morgoth and rescue the overmatched and defeated Elves and Edain, The Host of Valinor made war upon Morgoth and destroyed his armies.
Facing final defeat, Morgoth unleashed his last and greatest weapon; a fleet of winged fire drakes, led by Ancalagon. So terrible was their onslaught that the armies of the Valar were driven back from the gates of Angband, and their coming was said to have been accompanied by a tempest of fire and lightning.
But Eärendil came out of the West in his blessed ship Vingilot, accompanied by "a myriad" of the Eagles of Manwë led by Thorondor. The Eagles and Eärendil dueled with Ancalagon and the other dragons for a day. Eventually, Eärendil was victorious, casting Ancalagon down upon Thangorodrim and destroying the volcanic mountains in his fall. The death of Ancalagon marked the end of Morgoth's final resistance.
Gandalf spoke of him as he told Frodo the true origin of his Ring. "It has been said that dragon-fire could melt and consume the Rings of Power, but there is not now any dragon left on earth in which the old fire is hot enough; nor was there ever any dragon, not even Ancalagon the Black, who could have harmed the One Ring, the Ruling Ring, for that was made by Sauron himself."
Ancalagon's size is not specified, but must have been colossal due to the destruction of "the towers of Thangorodrim" when he fell on them, which are elsewhere identified with the three smoking peaks of those mountains.However, his size cannot be assumed to be larger than Thangorodrim; some powerful but comparatively small creatures are able to cause great destruction even in death, such as Durin's Bane breaking the slopes of Celebdil.
Like all other Urulóki, Ancalagon breathed fire, which was implied to be hotter than any other dragon's flame.
