Castamir the Usurper

Castamir is a lord of Gondor in the appendices to The Lord of the Rings, remembered by the name the Usurper. His parents are not recorded, but his grandfather is Calimehtar, younger son of King Calmacil, so that he stands within the royal house without standing in the line of succession. That descent and his standing win him the office of Lord of Ships under King Valacar. When Valacar's son Eldacar comes to the throne, many in Gondor object that the new king is only half of Númenórean blood, his mother having been of the Northmen, and Castamir turns that grievance to his own use, raising rebellion in the year 1437 of the Third Age and taking the crown for himself.