Mary "Zed" Martin is an artist who had visions of John Constantine. After meeting him in Heddwich, Zed began working with John with her psychic powers.
Mary had been born to a leader of the cult known as the Ressurection Crusade. One day, Mary ran away and had been on a run from them since. To avoid drawing attention to herself she stopped using her real name and started going by the name "Zed".
With her psychic powers, she began seeing visions of John Constantine and drew sketches of him.