In the conceptual world of Greek polytheism, divinities took part of their character from the realm where they dwelt. The gods who lived in heaven were sometimes known as Olympian, while those whose abode was subterranean were considered chthonian, from chthon, earth. The powers under the earth, not surprisingly, included the heroes and heroines, who exerted influence from their tombs, and the dead themselves, as well as the gods and goddesses who ruled and interacted with the dead. Overlapping with this group because of their shared relationship to the earth are the agricultural deities. Demeter and Persephone afford the best example of divinities concerned with both souls and crops. Equally, the heroes and other chthonians, such as the Athenian Semnai Theai (Reverend Goddesses) or Eumenides (Kind Ones), have the power to affect agricultural prosperity. Chthonians tend to have dual personalities and manifestations, alternately beneficent and hostile. Their “true” names are often avoided in favor of euphemisms.
Traditional scholarship made the Olympian/chthonian opposition parallel to others, such as Indo-European/Mediterranean, Greek/prehellenic, or even patriarchal/matriarchal. None of these juxtapositions can withstand critical scrutiny, especially given that the categories of Olympian and chthonian themselves cannot be used to construct a rigid classification of supernatural beings. First of all, the traditional Olympian gods have decidedly chthonian personalities in certain cults. Zeus Meilichios (the Mild) is an underworld counterpart of heavenly Zeus. Even an “Olympian” deity such as Athena Polias at Athens may have chthonian features, such as her association with the snake, a creature symbolic of the earth. Second, some deities evolved a cultic personality that blended Olympian and chthonian elements (the hero-gods Asklepios and Herakles are good examples), while others (such as the river gods and nymphs) can be comfortably assigned to neither category.
The other traditional assumption about the Olympian/chthonian distinction is that it corresponds to differences in sacrificial practices and terminology: in an Olympian sacrifice (generally termed a thusia), for example, the victim is light in color, the ritual is conducted in daylight on a raised altar, and the participants joyfully share in the meat. In a chthonian sacrifice (denoted by enagismos and other terms), the victim is black or dark, the somber sacrifice is performed at night on a low altar or over a pit, and there is no meal: the animal is burned completely. Chthonians are also thought to prefer wineless libations of milk, honey, and water. These generalizations fail because many supernaturals with a strong chthonian character, especially the heroes, regularly received festive, participatory sacrifices. In the study of Greek cults, it may be preferable to abandon the concept of a strong opposition between Olympian and chthonian deities, since the character of a given deity depends upon the context. The term “chthonian” remains useful as a marker for a set of divine characteristics and ritual acts which are more often than not found together, and which connote relations with the land, the dead, or the underworld.