[PapaBear3625]

Of course all it would take is the Knight King and a few dead zombies to cross to the Iron Islands on one ship then every new dead person would rise as a Knight King zombie until all living humans were eventually eliminated.

Knight King does not need a ship. He has a flying dragon.

He does not need zombies. He re-animates the dead by himself. All he needs to do is land at any island, kill a few, re-animate them, and the process starts over.

[LibertarianLiz]

He does not need zombies. He re-animates the dead by himself.

Yes, which is why I am a bit worried about them sending all of the non-combatants into the "crypts" to keep them safe.