Chthonian

Consus, moreover, is regarded as a god of the lower world, or Chthonian divinity—another circumstance which connects him with Poseidôn, whose character becomes more and more Chthonian the farther his cultus is traced into the East, where also his phase as lord of knowledge and wisdom appears more manifestly.

...I intend to apply the name chthonian to all gods and spirits of the earth, whether their functions are concerned with agriculture or with the grave and the world beyond, or (as often) with both.

The Olympian religion is truly Olympian when it rests on Chthonian grounds, and the Chthonian religion is truly Chthonian when it stands in the Olympian light.

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.

For example, the Oresteia, 'that treasure house of chthonian concepts' (Scullion 1994: 111), categorizes gods in ways that do not match the rigid terms of the foundational scholarship on Olympian versus chthonian deities.