The King hasn't 'left' to join the Ytharien. He's kind of a naive kid, defying his crown like he'd defy his parents, not a traitor to his own regime who convinces Knights to abandon the castle. All it is is a childish little fieldtrip, which is why the court of magistrates is annoyed and not panicked.

Also, I'm afraid the idea of a Knight-turned-Ytharien also wouldn't keep in the spirit of the Knights OR the Ytharien. It's important to know that the Ytharien aren't an infamous warband, but one of many elven groups. They're only significant at the moment because Alonso is buddies with them, but he's undercover.

Sorry you couldn't do your idea! As I said before, it's first come first serve, and I need to be sure I can rely on posters to follow through in a timely fashion.