It all started in Summerhall. Aegon The Unlikely’s attempt at resurrecting the Dragons was successful but at the cost of his life. The fire was able to be put out, not before it took Aegon V's life as well as his son, Ser Duncan The Tall, and a few rooms.  Ever since then, the events that decide the fate of Westeros had vastly changed. Dragons had returned; it was said that during the night of the fire, a bright crimson comet was seen in the night sky.  During the end of King Aerys’s reign, a Rebellion started. But it wasn’t started by Robert Baratheon due to Rhaegar’s actions. Robert instead fought for the Targaryens and was married to a Princess which resulted with them having a son, Rhaegon. Rhaegon Baratheon is the rider of Morghul, a massive Black Dragon that Hatched at the end of the Rebellion started by the River Dragon. He was not just named after the Dragon that was bound to Aegon III's first wife and cousin, Jaehera but because of Rhaegon's unique sense of humor as he inherited his mother's spirit.