In the middle was the palace of Hades, the king of the underworld, where he was seated upon a black ebony throne. Black was one of the most essential colors utilized by historical Greek artists. In the 6th century BC, they started making black-figure pottery and later purple determine pottery, using a highly authentic technique. In black-figure pottery, the artist would paint figures with a shiny clay slip on a purple clay pot. When the pot was fired, the figures painted with the slip would turn black, in opposition to a purple background.