The Keres are female personifications of violent or cruel death, including death in battle, by accident, murder or ravaging disease. Another being, Thanatos, was the god of non-violent death.
They were agents of the Moirai (Fates), goddesses of fate who measured out the length of a man's life when he first entered the world, and Moros (Doom) the god who drove a man towards his inevitable destruction.
The Keres were lustful of blood and feasted upon it after ripping a soul free from the mortally wounded bodies and sending it on their way to the Underworld. Thousands of Keres haunted the battlefield, fighting among themselves like vultures over the dying. The Keres had no absolute power over the life of men, but in their hunger for blood would seek accomplish death beyond the bounds of fate. Zeus and the other gods, however, could stop them in their course or speed them on.
The Olympian gods are often described standing by their favorites in battle, beating the clawing death spirits from them. Some of the Keres were personifications of epidemic diseases, which haunted areas riven by plague. The Keres were depicted as fanged, taloned women dressed in bloody garments.