One of the Fire & Blood storylines that we expected in House of the Dragon Season 2 was the fight of the Cargyll twins. That happened in Episode 2, but there are questions about the ending of the fight.
The episode saw Arryk Cargyll sent to Dragonstone to pose as his brother. That would have been find had it not been for Mysaria. She realized that Erryk was already in the castle, and she was able to alert guards to the plot about to happen.
Erryk got to Rhaenyra’s room in time to prevent his brother killing her. It led to a fight to the death, but which one fell on his own sword?
Nobody in Dragonstone could tell the twins apart in House of the Dragon
One thing that was clear throughout House of the Dragon Season 2, Episode 2 was that nobody in Dragonstone was able to tell the twins apart. The only reason Mysaria knew there was something going on was because she knew Erryk was in the castle. If it wasn’t for that, Arryk would have gotten away with the plot.
During the fight, another member of Rhaenyra’s guard even asks which twin is which. He couldn’t tell, meaning that he had to stand by and protect Rhaenyra while the brothers fought.
In the end, it looked like Erryk stabbed and killed his brother Arryk. He then turned to Rhaenyra, said “Your Grace, forgive me,” and killed himself by falling onto his sword. He was so taken with grief that he couldn’t live with himself after killing his brother.
It is possible that it was Arryk, though. The leg and arm wounds on him certainly looked like the ones Arryk sustained in the fight, but it is very hard to tell. Why would Arryk get the job done when he had the chance? Well, there was someone else there to protect Rhaenyra, and he was overtaken by grief of killing his brother.
While the moment was reminiscent of The Hound killing The Mountain in Game of Thrones, there was one major difference: love. The Hound and The Mountain hated each other. The Cargyll twins loved each other, and the idea of having to kill each other was something neither relished. They were going to suffer with the knowledge they did that, so whichever killed their twin, they were always going to end up killing themselves afterward.
What's not clear is which twin killed himself. It was likely Erryk, but the injuries suggest Arryk.