1. Caswallawn ap Don: son of Don and Beli, usurper of Caradawg ap Bran and Manawyddan ap Llyr, he is said to have killed the companions of Caradawg by doning a cloak of invisability. Caradawg died of a broken heart, and Caswallawn stole the throne from Caradawg's uncle Manawyddan, rightful heir to the throne of Prydein (Britain).
2. British chieftain who fought off the Roman Empire but was defeated; he is later confused by medieval chroniclers with a mythological figure by the same name--Cassebelannus, as is Caractacus with Caradawg ap Bran.