Drogon was one of the dragons born in the Dothraki sea. Commanded by Daenerys Targaryen, he was named for her dead husband, Drogo. Drogon was believed to be the reincarnation of Balerion the Black Dread, die to his size and colouration. The largest and most aggressive of Daenerys's three dragons, Daenerys had problems reining him in, and all later attempts but one ended in death.
Drogon was the last dragon of House Targaryen.
Drogon's scales were black, his horns and spinal plates were blood red, and his eyes were smouldering red pits. His teeth were black as well. His flame was black fire shot with red and the wash of its heat could often be felt thirty feet away. His wing flap sounded like the clap of thunder, and he bled black blood.
Though a strong and swift-growing beast in his younger years, long periods in the Red Mountains of Dorne stunted Drogon's growth, stopping him from ever winning his full size. By his death he was only a middle-weight, when compared with the skulls and records of dragons past.
Drogon was born upon the funeral pyre of Khal Drogo, along with his two egg-mates Viserion and Rhaegal. All three were hatched by and later served Daenerys Targaryen, whom men called the Mother of Dragons, traveling with her across Essos in her attempt to claim the Iron Throne.
Drogon was the largest and most unruly of the Stormborn's beasts, quickly outsizing his two siblings. When at last Queen Daenerys crossed the Narrow Sea in 301AC, she did so on the back of Drogon, and used him primarily in combat. After her death at the hands of the Dornish Drogon fled into the Red Mountains, remaining there for several decades.
The mountains of Dorne proved too treacherous for any concentrated attempts on the beast to be made, and the combination of heat and ready caves lent the area to serving as a dragon's haunt. Often Drogon would swoop down on either side of the bluffs, taking cattle or horses into his jaws and devouring them. Sometimes he would remain for a while - others would seem him swiftly wing away again, heavy beats of leathery wings taking him upward faster than an arrow might follow.
Of course, the allure of a dragon was mighty, and many an adventurer saw themselves as the next Aegon the Conqueror, if only they might harness the beast. Travelers from across the known worled traveled to Dorne to visit it's Red Mountains, hoping to tame the beast. Archons, Magisters, Princes and Kings - even smallfolk and dragonseeds all tried their hands, perishing one and all in a wreath of fire and a roar. In the end it was Baelon Targaryen, son of King Aegon Targaryen who tamed the beast - and with it, he wrought great and terrible harm upon the kingdom of Westeros during the War of the Shadow.