Tywin Lannister: I grant you, it was done too brutally. Elia need not have been harmed at all, that was sheer folly. By herself she was nothing.
Tyrion Lannister: Then why did the Mountain kill her?
Tywin Lannister: Because I did not tell him to spare her. I doubt I mentioned her at all. I had more pressing concerns. (…) Nor did I yet grasp what I had in Gregor Clegane, only that he was huge and terrible in battle. The rape…even you will not accuse me of giving that command, I would hope.
“Oberyn wanted vengeance for Elia. Now the three of you want vengeance for him. I have four daughters, I remind you. Your sisters. My Elia is fourteen, almost a woman. Obella is twelve, on the brink of maidenhood. They worship you, as Dorea and Loreza worship them. If you should die,must El and Obella seek vengeance for you, then Dorea and Loree for them? Is that how it goes, round and round forever? I ask again, where does it end?” Ellaria Sand laid her hand on the Mountain’s head. “I saw your father die. Here is his killer. Can I take a skull to bed with me, to give me comfort in the night? Will it make me laugh, write me songs, care for me when I am old and sick?”
Queen Myrcella? It would have been more tempting if only he did have Sansa tucked beneath his cloak. If she declared for Myrcella over Tommen, would the north follow? What the Red Viper was hinting at was treason. Could Tyrion truly take up arms against Tommen, against his own father? Cersei would spit blood. It might be worth it for that alone.