While the salt king commanded an island's ships whenever they were at sea, the rock king ruled the isle itself, dispensing justice, making laws and settling disputes. Each type of king was chosen at kingsmoots. An isle's rock king was usually older than its salt king. The two were sometimes father and son, and in some other cases they came from rival houses.
The tradition of rock kings ended when Urron Greyiron attacked the attendees of the kingsmoot deciding the successor to Urragon IV Greyiron. Urron Redhand made House Greyiron the hereditary Kings of the Iron Islands, and the rock and salt kings were reduced to lords or extinguished.
Known rock kings
The oldest surviving records at the Citadel reveal that each of the Iron Islands was once a separate kingdom, ruled by not one but two kings, a rock king and a salt king. The former ruled the island itself, dispensing justice, making laws, and settling disputes. The latter commanded at sea, whenever and wherever the island's longships sailed.—writings of Yandel