Ambrosius Aurelianus was a war leader of the Romano-British who won an important battle against the Anglo-Saxons in the 5th century, according to Gildas. He also appeared independently in the legends of the Britons, beginning with the 9th-century Historia Brittonum. Eventually, he was transformed by Geoffrey of Monmouth into the uncle of King Arthur, the brother of Arthur's father Uther Pendragon, as a ruler who precedes and predeceases them both. He also appears as a young prophet who meets the tyrant Vortigern; in this guise, he was later transformed into the wizard Merlin.

Vortigern, also spelled Vortiger, Vortigan, Voertigern and Vortigen, was a 5th-century warlord in Britain, known perhaps as a king of the Britons or at least connoted as such in the writings of Bede and Gildas. His existence is contested by scholars and information about him is obscure.