You're not going to serve. You're going to die
My father was an evil man. On behalf of house Targaryen I ask for forgiveness for the crimes he committed against your family. And I ask you not to judge a daughter by the sins of her father
I offer you a choice, bend the knee and join me. Together we will leave the world a better place than we found it. Or refuse and die.
Either you knew Cersei was lying and let me believe otherwise, or you didn't know at all. Which makes you either a traitor or a fool.