A scene from “Unfinished Business”

Viserys: There's something else that I need to tell you. It might be difficult for you to understand, but you must hear it. Our histories... They tell us that Aegon looked across the Blackwater from Dragonstone and saw a rich land ripe for the capture. But ambition alone is not what drove him to conquest. It was a dream. And just as Daenys foresaw the end of Valyria, Aegon foresaw the end of the world of men. 'Tis to begin with a terrible winter gusting out of the distant north. Aegon saw absolute darkness riding on those winds. And whatever dwells within will destroy the world of the living. When this Great Winter comes, Rhaenyra, all of Westeros must stand against it. And if the world of men is to survive, a Targaryen must be seated on the Iron Throne. A king or queen strong enough to unite the realm against the cold and the dark. Aegon called his dream "The Song of Ice and Fire." This secret? It's been passed from king to heir since Aegon's time. Now you must promise to carry it and protect it. Promise me this, Rhaenyra. Promise me.