Briseis, in Greek mythology, was the daughter of Briseus. She was taken captive by Achilles, but was taken by Agamemnon for his own, when the latter had to return Chryseis to her father Chryses, to end a plague sent by Apollo. Achilles and Briseis grew close, despite their situations, and treated each other as husband and wife. When Achilles lost her, he removed himself from battle. He only returned after the death of Patroclus and the return of Briseis.