chthonic powers

chthonic (THONE-ik), adjective:
dwelling in or under the earth; also, pertaining to the underworld

“Driven by dæmonic, chthonic Powers.” –T.S. Eliot

“The chthonic divinity was essentially a god of the regions under the earth; at first of the dark home of the seed, later on of the still darker home of the dead.” –C. F. Keary

“The chthonic imagery of Norine’s apartment, which..was black as a coalhole and heated by the furnace of the hostess’ unslaked desires.” –M. McCarthy

“Two great and contrasted forms of ritual: the Olympian and the Chthonic, the one a ritual of cheerful character, the other a ritual of gloom, and fostering superstition.”
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Chthonic comes from khthón, the Greek word for earth.

from Dictionary.com