When the men first come to Shelling village to recruit soldiers for their war with the Heathen, it is the first thing the children of Closti the Clam have ever heard about having a King. He evidently spends very little time on the River, and does little if anything for the villagers under his reign.
Late in the novel The Spellcoats, the King's soldiers capture the three youngest children, and bring them to the King, who is a pudgy, short man who is constantly smiling, and who at first doesn't believe the children are not Heathens, because of their light hair and darker skin. What finally convinces him is seeing their hearth gods, especially The One, who has just come out of his fire, and who appears to be solid gold.
The King tells the children that as King, he is told more than the average person, and he knows that in ancient times, The One put part of his power in that statue, with the requirement that he be put into fire every year. What the children don't know is the legend that when that statue turns gold, it means The One is at his highest level of power, and great things can be accomplished.
He decides to bring the children along, as guardians of The One. He is also interested in their oldest sister Robin, and remarks he has made about needing to marry again and father an heir make it clear to the other children that something needs to be done to save her.
Eventually the King turns out to be of some use to the children, but he is not an upright man, and a very poor king to his people.