Rhaenys Targaryen
Rhaegar's little daughter by Elia of Dorne, a small girl who loved her cat, lost in the fall of the Targaryen dynasty.
The fuller tale
Rhaenys was the elder of Prince Rhaegar’s two children by Elia Martell, a small dark-haired girl who took after her Dornish mother — a disappointment, reportedly, to her grandfather the king, who muttered that she smelled Dornish, whatever that can have meant to anyone but him. The books remember her almost entirely through one detail, which is somehow worse than a biography: she had a black kitten she named Balerion, after the greatest of the conqueror’s dragons, and she chased it through the halls of the Red Keep where the real Balerion’s skull hung in the dark below.
She was named for the boldest of the original three Targaryens — Rhaenys, the conqueror’s younger sister-wife, who rode Meraxes — and in the ordinary run of history she would have grown up a princess of the blended line her father seemed deliberately to be building: Targaryen and Martell, fire and sun. Rhaegar is said to have believed the dragon must have three heads, and named his daughter and son as if assembling the prophecy piece by piece. Whatever he meant by it died with him, and the children he left in the capital became, in the rebellion’s endgame, exactly what hostages always become.
In the tale she exists as a wound that will not close. Her name is the first thing Oberyn Martell says to a Lannister and nearly the last thing he screams at the Mountain; her death is the reason Dorne sits out Robert’s reign in cold fury, the reason Tywin’s pragmatism reads as monstrous even to his allies, and one of the reasons Ned Stark rode away from his king in disgust before their friendship was a fortnight old as a reign. The tale’s realists call the killing of Rhaegar’s children policy. The tale itself, rather insistently, calls it Rhaenys and Aegon.
The page and the screen
Neither telling stages her life; both inherit her death as history. The books are more precise about the horror — naming Ser Amory Lorch as the killer who dragged her from her hiding place, counting the wounds, and making Tywin’s cold apportioning of blame part of Jaime’s and Oberyn’s memories — while the show folds the deaths of both royal children into Oberyn’s accusations against the Mountain and Tywin, sanding off the specifics. The show also never mentions the kitten, which book readers will tell you, correctly, is the whole point of her. One further book-side ripple: the existence of a claimant calling himself her brother Aegon makes book-Rhaenys’s fate a live political question again, since everyone agrees the girl, at least, truly died.
Their fate — if death has found them, it is written here. Open at your peril.
Before the tale: Died in the Sack of King's Landing, before the story
Rhaenys died in the Sack of King’s Landing, before either telling begins, when Tywin Lannister’s men took the Red Keep in the rebellion’s final hours. In the books she hid beneath her father’s bed, and Ser Amory Lorch found her there: a knight in mail stabbing a screaming three-year-old, half a hundred wounds by the count that reached Dorne. Even Tywin, who ordered the children dead as proof of his new loyalty, is said to have judged the manner of it needlessly savage — his complaint, characteristically, was about presentation.
The bodies of Rhaenys and her baby brother were wrapped in crimson cloaks and laid before the Iron Throne as tokens for Robert Baratheon, who saw dragonspawn where Ned Stark saw murdered children — the first crack in the rebellion’s victory, and the seed of Dorne’s long grudge. The show keeps all of this as remembered history in Oberyn’s mouth; the books add the detail that no one in Dorne ever doubted Rhaenys’s death, however much they came to question her brother’s.