The Cannibal

" The largest and oldest of the wild dragons was the Cannibal, so named because he had been known to feed on the carcasses of dead dragons, and descend upon the hatcheries of Dragonstone to gorge himself on newborn hatchlings and eggs. Coal black, with baleful green eyes, the Cannibal had made his lair on Dragonstone even before the coming of the Targaryens, some smallfolk claimed. Would-be dragontamers had made attempts to ride him a dozen times; his lair was littered with their bones."
- Fire and Blood Vol. 1, George R. R. Martin