Game of Thrones, Season 3

Margaery Tyrell:
[to Cersei, as they prepare for the wedding] You look radiant, your Grace.

Cersei Lannister:
Radiant? Why radiant?

Margaery Tyrell:
It's word that came to mind. [Cersei smiles, though falsely, and Margaery takes her arm] We're going to be sisters soon, we should be friends.

Cersei Lannister:
You're a musical girl, aren't you? I imagine you have a lovely voice.

Margaery Tyrell:
A better dancer, than a singer, I'm afraid.

Cersei Lannister:
Ah, but you know the song, the Rains of Castamere?

Margaery Tyrell:
Of course. They play it so often here at court.

Cersei Lannister:
So you know the story of House Reyne of Castamere?

Margaery Tyrell:
Not as well as you, I'm sure.

Cersei Lannister:
House Reyne was a powerful family. Very wealthy. Second wealthiest in Westeros. Aren't the Tyrells the second wealthiest family in Westeros now? Of course, ambitious climbers don't want to stop on the second highest rung. If only you could take that final step. You'd see further than all the rest. You'd be alone with nothing but blue sky above you. So Lord Reyne built a castle, as grand as Casterly Rock. He gave his wife diamonds, larger than any my mother ever wore. And finally, one day, he rebelled against my father. Do you know where House Reyne is now?

Margaery Tyrell:
Gone?

Cersei Lannister:
Gone? [menacingly] A gentle word. Why not say slaughtered? Every man, woman and child, put to the sword. I remember seeing their bodies hanging high above the gates of Casterly Rock. My father let them rot up there all summer. It was a long summer. [Quoting "Rains of Castamere] And now the rains weep o'er their halls, and not a soul to hear." [Takes Margaery's hand, looks into her eyes, and speaks in a cold tone] If you ever call me "sister" again, I'll have you strangled in your sleep.