The Stallion Who Mounts the World is a Dothraki prophecy. According to the prophecy, the Stallion will unite all the Dothraki into a single khalasar under a single khal and ride to the ends of the earth. He will be the khal of khals, and all the people of the world will be his herd.
Daenerys Targaryen’s unborn son, Rhaego , was believed to be the prophesized Stallion but he was killed in the womb before any part of the prophecy could be fulfilled. The Lhazareen witch, Mirri Maz Duur , believed that his birth would cause unbridled death and suffering. She tricked Daenerys into sacrificing the life of her son for the life of her husband, khal Drogo .