Drowned Ammet

"Set in the repressive south of Dalemark ... it features all new characters." The boy Mitt has been raised to avenge his disappeared father, believed to have been betrayed by fellow revolutionaries. Mitt bombs the festival of Old Ammet and Libby Beer, forgotten figures of folklore whose effigies are annually delivered to the sea. He escapes by sea with the Earl's two grandchildren, and they learn something of Ammet and Libby during a great storm. --quoting and gleaning from Kirkus Reviews 1978-03-01 (above, posted 2012 with later cover image and ISBN)