Rhaego

In Vaes Dothrak, the elder women of the dosh khaleen read the omen and declared that Drogo and Daenerys's son would be the prophesied rider, and gave him the name of her dead brother. Drogo, proud, vowed to one day set him upon the throne his grandfather had held and conquer the Seven Kingdoms in his name.

But a wound of Drogo's turned foul, and Daenerys sought out the maegi Mirri Maz Duur to save him. The ritual left Drogo alive but empty of mind and will, and in exchange it claimed the child growing inside Daenerys: he was born already dead, and Mirri Maz Duur described him as deformed, scaled, and rotted within, as though long dead already.

Feverish after the birth, Daenerys dreamed of the son she would never have: tall and proud, with skin bronzed like Drogo's and hair of gold and silver like her own, smiling and reaching out a hand to her before he breathed fire and was consumed whole, until nothing remained but ash.

In the House of the Undying, among her visions, Daenerys beheld a tall man with copper skin and hair of gold and silver, standing beneath the banner of a burning stallion with a city aflame behind him: the image of what Rhaego might have become had he lived.

Years later, in Daznak's Pit, after watching a massacre unfold, Daenerys remembered eating a horse's heart to give her unborn son strength, and how it had not been enough to save him from Mirri Maz Duur. She remembered too the words of the Undying about three treacheries, and counted Mirri Maz Duur's as the first and Jorah Mormont's as the second, wondering whether she had already spent them all. Soon after, Drogon appeared in the sky above the pit.