Erryk Cargyll

Erryk already wore the white cloak of the Kingsguard in the service of Viserys I, holding the same post as his twin brother Arryk. At the tourney of Maiden's Pool, Ser Criston Cole unhorsed him.

After Rhaenyra's sons clashed with Aemond Targaryen at Driftmark and Aemond lost an eye in the fight, King Viserys ordered the princess back to Dragonstone with her children. He also decreed that her sworn shield would no longer be Ser Harwin Strong, who was sent back to Harrenhal, but Ser Erryk instead.

After the death of Viserys I in 129 AC, Erryk followed the same path as Ser Steffon Darklyn and Ser Lorent Marbrand: he sided with the Blacks and joined Rhaenyra's Kingsguard at Dragonstone, where he also sat on her Black Council. His brother Arryk went the other way, staying with King Aegon II and the Greens in King's Landing.

The two brothers no one could ever tell apart now stood on opposite sides of the same war.

Arryk was part of the escort when Grand Maester Orwyle traveled to Dragonstone to negotiate with Rhaenyra. A song composed long after the fact claims the twins tried that day to talk each other into switching sides, and that when it failed they parted with words of love, knowing the next time they met it would be as enemies; no record from the time confirms it.

After the murder of Prince Jaehaerys, Aegon II's son, the king wanted revenge. Ser Criston Cole, now Lord Commander of his Kingsguard, ordered Arryk to slip into Dragonstone disguised as Erryk. Whether his target was Rhaenyra or her children is disputed. He reached the island dressed as a fisherman, put on his white armor and cloak underneath, and walked into the castle unchallenged, until on his way to the royal chambers he came face to face with his own brother.

Erryk understood at once why his brother was there, and the two drew their swords. Accounts of what followed do not agree: Septon Eustace says only that the Cargyll twins killed each other. The bards sing that they professed their love as they drew steel. Munkun's Dance of the Dragons describes a fight lasting nearly an hour that woke half the court, none of whom could tell one brother from the other even watching; in that version they died together, mortally wounded, weeping in each other's arms.

Mushroom's testimony gives a much shorter fight, with no declarations of love: they called each other traitor instead. There, Erryk lands the first killing blow, nearly severing Arryk's arm at the shoulder, and Arryk, already falling, pulls his brother's cloak close to stab him in the belly with a dagger. Arryk was dead before anyone found them. Erryk took four days to die of that wound, cursing his brother and screaming in pain the whole time.

Erryk and Arryk were physically identical, so much so that not even their fellow Kingsguard could tell which was which just by looking at them.