In The Grove of the Oracle. GIF by The Current Sea, 2015.
The Pythia, commonly known as the Oracle of Delphi, was the name of any priestess throughout the history of the Temple of Apollo at Delphi. Established in the 8th century BC, Pythia was widely credited for her prophecies inspired by being filled by the spirit of god Apollo.
The usual theory has been that the Pythia delivered oracles in a frenzied state induced by vapors rising from a chasm in the rock, and that she spoke gibberish which priests interpreted as the enigmatic prophecies preserved in Greek literature.