The Viper and the Mountain by DrBrunch. Oberyn Martell and Gregor Clegane. "When the two men were ten yards apart, the Red Viper stopped and called out, 'Have they told you who I am?' Ser Gregor grunted through his breaths. 'Some dead man.' He came on, inexorable."
King Gerold II Lannister - Tyrion III and Gerold II were being worn down slowly by wave after wave of Andals over the years, and seeing that total resistance was doomed to failure, decided to make alliances with different Andals to preserve their family and lands as best they could. Both Tyrion III and Gerold II married Andal wives, awarded lands to other Andals, and exchanged wards with others. Afterwards the Lannisters and the Westerlands became dominated by Andal culture.