The Keres (Κἣρες) were death spirits, and they resembled the Erinyes (or Furies): female, with fangs and talons. They were said to carry off the dead to the Underworld.
Apart from Hesiod's work, I've failed to find any reference from other sources.
Erinyes (or Furies).
By Jimmy Joe
Female spirits who punished offenders against blood kin. The Erinyes (Ἐρινύες) were named Alector, Tisiphone and Megaera. They were born together with the Giants and the Meliae, from the earth where blood landed from the severed genitals of Uranus...
Cerberus was the three-headed hound that guarded the gate to Hades. According to the Theogony, Hesiod said that Cerberus had fifty heads. Cerberus was the monstrous offspring of Typhon and Echidna. Cerberus was to keep the dead or shades from retu...
Goddesses of fate. The Fates or Moerae (Moirai) were known by Hesiod as the three daughters of Nyx ("Night"): Clotho, Lachesis and Atropos. In later accounts they were known as daughters of Zeus and Themis, and possibly sisters of the Seasons (Hor...
The thought of Nergal as the god of death has been an extremely frightening idea for every man in ancient Mesopotamia. You surely don’t want to talk about death or the afterlife or even give a hunch about the presence of Nergal, the Lord of the Un...
A group of winged women. There were said to be only two harpies: Aello and Ocypetes, the daughters of Thaumas, the son of Pontus and Gaea, and the Oceanid Electra. They were the sisters of Iris. Later writers said there was a third Harpy. The best...
A chthonic god of the underworld. Heros was frequently depicted on funerary stelae as a horseman.
The Fylgjur were female protective spirits where each fylgja attached herself to an individual at birth. The fylgja remained with that person for the rest of his or her life. At the person's death, the fylgja would attach to someone else. In this ...
The following beings come from the spirit world. Some were protective spirits or minor deities. Note that Valkyries have been moved to a new page of their own.
Aericura was a chthonic god of the underworld. Aericura was a Romano-Celtic (Gallic) god known only from inscriptions.
The Gorgons, Γοργόνες, were perhaps the strangest of the monsters that appeared in Classical mythology. They were winged women with snakes on their heads instead of hair. A single glimpse of their hideous visage would turn any creature, mortal or ...