Artesia

In the Elizabethan play The Birth of Merlin, the sister of the Saxon general Ostorius.

She used her wiles to cause strife between King Aurelius Ambrosius of Britain, to whom she was affianced, and Uther, who was enamoured of her, by seducing Aurelius, blinding him to the gradual Saxon invasion of his kingdom.

Uther Pendragon discovered her treachery, but she managed to have Aurelius banish his brother from court. In the end, Artesia and her brother betrayed and murdered Aurelius. When Uther reclaimed the kingdom, he had Artesia executed.