Arryk Cargyll
A knight of the Kingsguard, twin to Ser Erryk — two white cloaks cut from one cloth, sworn to a crown that split in half beneath them. Arryk's half stayed green.
A soul born at Crackclaw Point, sworn to The Greens — the King's Party, The Kingsguard.
The fuller tale
Season Two
Ser Arryk Cargyll is sent to Dragonstone wearing his twin's face; Ser Erryk finds him at Rhaenyra's door.
Where they stand. Dragonstone.
Their story
A knight of the Kingsguard and twin to Ser Erryk, Arryk is cut from precisely the same cloth as his brother — same face, same training, same white cloak — and finds himself, by the accident of which royal household each twin happened to be serving when the crown split, sworn to the green faction while his brother serves the black.
The war asks something of the Cargyll twins that it asks of almost no one else: Arryk is sent by the Hand on a mission that requires him to use his own brother's face as a weapon, infiltrating Dragonstone disguised as Erryk in order to reach the queen herself.
How it ends for them
On the screen. Slain by his twin at Dragonstone (S2·E2)
The Hand sent him to Dragonstone wearing his twin brother's face to murder the queen. Erryk found him at her door: twin fought twin by candlelight, an hour of steel between men with one face, until Arryk died on his brother's sword.
On the page. Slain by his twin at Dragonstone (F&B, ch. 3)
Ser Criston sent him to Dragonstone in a black cloak to kill or steal the queen. His twin met him at the gates. They fought, says Gyldayn, for the better part of an hour, weeping as they fought — and died in each other's arms, each begging the other's pardon.
In the show, Erryk recognizes his brother despite the disguise before Arryk can reach the queen's chambers, and the two fight at Dragonstone's gates until Arryk falls on his brother's blade.
Fire & Blood's account agrees on the setting and the outcome but lingers longer on the duel's anguish — the brothers fighting for the better part of an hour, weeping throughout, before Arryk dies of the wounds Erryk deals him, each begging the other's forgiveness as the fight plays out.
Their chapters, book by book
Where the page and the screen part
Both tellings put the brothers' final duel at Dragonstone and agree on its emotional shape — two men with one face killing each other for causes neither entirely chose. Fire & Blood adds a detail the show's tighter staging omits: Gyldayn records the duel lasting the better part of an hour, with both brothers reportedly weeping even as they fought, unable to fully commit to killing the person who was, for their whole lives before this war, effectively the same person as themselves.
Their journey
Where the two tellings send them to the same place the road runs whole; where they part, the screen keeps the left and the books the right.