The Cannibal was a great black dragon, never claimed and never ridden, that made his lair in the high caves of Dragonmont long before the Dance of the Dragons. He earned his name by his appetite: smaller dragons, newly hatched dragons, the eggs of dragons in their cradles; all were the Cannibal's prey. The Targaryens left him to his caves.
During the Dance the Cannibal was already old, and the seed seekers who came to Dragonmont avoided his domain by long custom. After the war ended, when the last claimed dragons died and the great dragonpit at King's Landing fell, the Cannibal is said by some maesters to have flown east and never returned. No skull was ever found. His fate is unknown.