Carl Sagan: "I'm sorry; I thought you said, "the fifth cardinal direction.""
Robo: "I did."

— on the Zorth axis, "Atomic Robo Vol. 3"

The Zorth axis is a theoretical fifth cardinal direction mentioned multiple times in the Atomic Robo comic series. It was first developed by Robo when he was, for unknown reasons, hyperspatially curled up in the other four cardinal directions in 1967. Though there is no proof supporting a fifth cardinal direction, Robo insists that it was the most significant cartographic discovery since longitude, and was able to create complex higher-dimensional mathematic equations with the theory, proving to be of some effect a number of times: once when attempting to imprison The Shadow From Beyond Time in 1971, and another time when imprisoning the unknown Odic entity during 1999.