Things have been gloomy in Casterly Rock since Tyrion came back from Starfall with three corpses to bury and no bride to wed. His aunt and her family decided to spend some time in the Twins, her husband's birth home, and Aunt Dorna (Uncle Kevan's wife) left for her own ancestral home with her remaining children. A few Lannisters remain in the Rock, but they are distant both in blood and bond, so he is essentially left alone with Myrcella and Tommen.
Fortunately, Ser Addam answers to his summoning and comes to the castle to help with the children's training. Metalbending was the one thing his niece and nephew had left that belonged to themselves, and Tyrion would hate to let them lose it too.
A sweetheart as always, Myrcella offers him whatever comfort she can. She brings him to the mines when he isn't busy with his duties, keeps him company in his reading with a book of her own and offers to help with some of his duties. Perhaps she expects to inherit the Rock now that I have no weddings on the horizon, he thinks for a moment, but quickly dismisses it. Myrcella has always been aware she'd never inherit a thing, even when she was a princess. After all, in the event that Robert, Joffrey and Tommen died before her, she'd only get the crown if her uncles also died without male heirs. She can't expect to get the Rock with Tommen in the picture, and he highly doubts she'd kill him.
Once, they receive a letter from King's Landing asking for Jaime's whereabouts, as he is accused of conspiring with House Stark to hide Prince Rhaegar's bastard son as Jon Frost, Ned Stark's own bastard, who is supposedly the Avatar. His first reaction is to laugh, but it dawns on him the story is not far-fetched when you consider what is known about the rebellion and Lyanna Stark's fate. Still, he brushes the matter aside; if all of this is true, there is nothing he can do about it. Instead, he burns the letter and replies to the capital saying he hasn't heard news of Jaime since he was sentenced to the Night's Watch, and that he wasn't at the Wall when he went there.
Sometime later, he gets another letter from the capital, this time bearing the news of Robert Baratheon's murder and his baby daughter's hushed coronation. And then, a week later, he receives two letters from Myr, and those reveal to be extremely relevant to him and House Lannister.
The first thing he checks is the letters' signature: both are from his exiled sister. He tells the servant to fetch Myrcella and Tommen and begins to read the longer one.
To the Lord of Casterly Rock,
I write to you, dear father, not as a mere exile anymore, but as Hand of Queen Daenerys Targaryen, First of Her Name, Queen of the Seven Kingdoms—well, you know all the titles.
The mention of Father saddens him briefly, but his grief is soon replaced by how Cersei addresses herself. The titles themselves already tell quite the story: somehow, Daenerys Targaryen, the baby girl who barely escaped Dragonstone in time to avoid being killed by Stannis Baratheon, gathered enough power and influence to call herself Queen, and Cersei supports her and made her way inside her Small Council. Tyrion is very intrigued, to say the least.
You may be wondering if I've finally gotten mad, given everything you must have heard of me after my exile—gods only know what rumours have circulated. I do hope you've only trusted Tyrion's word; he's your only trustworthy source on what happened in Winterfell.
He lets out a small smile at the praise, even though Cersei is being pretty much factual—he is the only reliable witness who made it to Casterly Rock. The children were kept in the dark for most of the time, and so was the Hound.
Well, this matters little now. What matters is this: soon after I arrived in Pentos, I met, by chance, with the exiled Targaryens. After all I've been through at Robert's hands—you don't know half of it, I think only Jaime really does—I wondered whether Aerys wasn't an unfortunate exception, and whether the Iron Throne should return to House Targaryen after all.
With this in mind, I established an alliance with Viserys and Daenerys Targaryen by marrying the former, on the same day the latter wedded a Dothraki khal. Both of our husbands came to die, although at different times and under completely circumstances, but Daenerys was the one I grew the closest to.
Daenerys Stormborn, she's called due to the day of her birth, but she's truly a storm—in the best possible way. She stands up to what she thinks it's right, even putting her life at risk—and her values are in the right place. After her husband's death, she inspired so much loyalty that, for the first time in known history, the Dothraki kneeled before a woman.
His reading is interrupted by the children's arrival. "Your mother sent letters," he explains. "I'm reading one of them, and I'll hand it to you as soon as I finish it, but she seems to be doing well."
Myrcella and Tommen smile, but sit dutifully across him and stay quiet as he progresses. The next words nearly make him fall off his chair.
...Although I must admit, it wasn't just Daenerys herself that drove the men to bow to her. On her husband's funeral pyre, she placed dragon eggs gifted to her on her wedding. She's a firebender, taking after her mother instead of her father—and I have seen enough of her to be sure she is more Rhaella's daughter than Aerys'.
The dragons hatched. No, I'm not japing. As I write, there are three tiny dragons playing with one another, learning to breathe fire. Daenerys' firebending improved exponentially after the hatching, and her people follow her faithfully—not blindly, but aware that she has their best interests in mind.
Seven hells. Dragons reborn! He's tempted to throw the missive in the fire and call his sister a madwoman, but, deep down, this information makes him believe her more. Cersei is many things, but insane is not one of them; she'd not speak of dragons if she hadn't seen them with her own eyes.
I know nothing about the current situation in Westeros, but, given Robert no longer has heirs and it will be a while before he gets those, I doubt it's stable. When Daenerys comes, I wish for you to side with us. I'm already Hand of the Queen, which will grant our House ample protection if you bend the knee to her.
Although her reign has just begun, I'm proud to serve Queen Daenerys, and so will you be.
He takes a deep breath as he hands the letter to his niece. It's a lot to think about already, but he won't make any decision before reading the second one, so he unrolls it.
To Lord Tywin Lannister,
Father, I bear good and bad news, both related to each other. As I made my way to Myr, from where this letter is being sent, I found out about a man who was 'waiting for a Lannister to arrive'. Of course, I was suspicious, but I got enough information to deduce this man knew Uncle Gerion. Hope drove me to his house.
Sadly, your brother is indeed dead. He made it to Old Valyria and left it alive, but terminally ill, and died a month after his arrival in Myr. However, he left a heirloom: Brightroar.
Yes, Uncle Gerion found our House's ancestral sword! Its pommel matches the drawings we have in the Rock, and Uncle's friend spilled Jaime's name as the one he was expecting to deliver the sword to, so there is no reason to believe it false. I'm safekeeping it for now, to deliver back to the Rock after Daenerys conquers her throne.
His breathing is slightly erratic by the time he finishes it. Uncle Gerion succeeded in quest to find Brightroar! For years, Father has treated him as dead and his mission a failure, much to everyone's chagrin.
Myrcella's voice brings him back to reality. "Are you going to support this new queen, Uncle?"
He takes a deep breath to calm his nerves. "I have to think about it," he admits, "but I'm inclined to do so, yes. Especially after this second letter." He hands it to her.
Tommen squeals in delight after hearing Brightroar was found. Tyrion has no idea how the young boy knows about the sword, but he's too happy about the discovery to actually care.
He writes to Aunt Genna, reporting Cersei's tales, and calls for his remaining cousins. When Damion speaks in favor of supporting Daenerys, the rest of the family agrees, and Tyrion ultimately decides for it.
There is little reason to think Cersei's letters to be false. He can't think of anyone in Essos who would go through the trouble of learning to imitate her handwriting and write to the Rock about Queen Daenerys Targaryen, dragons and Brightroar. Those stories don't mix together all that well, which means few people would try it unless they mean it.
Not to mention the huge risk Cersei ran when she wrote and sent these letters. She knows as well as anyone else that Robert was set to kill all Targaryens—he didn't want to spare even the Avatar. Had this letter been intercepted and read by a Baratheon supporter, she'd be hunted and killed in no time. She would not run such a risk if her words were not true. All in all, he firmly believes his sister to be telling the truth.
Now he has to think about what this support means. These letters came from a Myrish mailing post, meaning he has nowhere to reply to—and, for all he knows, Cersei is no longer in the city. He cannot write to her confirming his support, so what can he do?
I could send someone to find her and pledge support in my name, he thinks. A man to serve in the Queensguard, perhaps, or a woman to serve as Daenerys' handmaiden. But who?
His cousins are either married or too young to make the voyage, and sending distant kin may backfire, as Cersei might have forgotten about them after spending fifteen years in the capital.
Another issue comes to mind as he ponders over the matter: Daenerys needs support from other kingdoms aside from the West. It is possible that the North favors her after all that has gone on between House Stark and the Crown, but even that is uncertain. The Iron Islands don't care for anyone other than themselves, and Tyrion has no interest in dealing with them after the attack that ended in Joffrey's death. The Reach is tied to the Baratheons; Margaery married Robert, birthed a daughter of his seed, and yesterday Tyrion was invited to the wedding between her and Queen Arwyn's regent Renly. The riverlands' loyalty depends on the Starks', he thinks, and the Vale is a huge question mark. The stormlands are an obvious no, and Dorne…
Dorne might just work, he thinks. If anyone would be interested in bringing the Baratheon dynasty down, it's Doran Martell. Still, it's a delicate matter; if he tells him about Daenerys and he doesn't lend support, he will have fed the opposition with precious information.
It's still his best bet, though, so he decides to try it. He finds Myrcella and Tommen in the mines and announces they are going to Sunspear within a moon turn. As they show their excitement for the trip, he wonders whether one of them would be a good option to send to Cersei. She'd love to see her children again, he thinks, and they'd be glad to meet their mother too.