The Keres were female death spirits in Greek mythology, daughters of Nyx, the goddess of the night, and Erebos, the god of darkness. They were the sisters of the three Moirai, the Fates, as well as other deities, including Nemesis, Oizys, Geras and Apate. They had a gruesome appearance and hovered over the battlefields in search of dying soldiers.
It may be that the Keres were connected to the Valkyries, which were war spirits of Norse mythology. They both flew over conflict areas searching for dying people; however, the Keres were malevolent spirits, while the Valkyries were benevolent ones, which may be a reflection of the stance towards war by the two cultures.
Keres Is also called Tenebrae, Ker.