Corthel was a gaseous substance with the ability to reflect light. Explorers residing on Draenell's Point, a planet within the Bissillirus system, came across Corthel on Nurstin, another planetary body in the same star system. This discovery occurred after they observed peculiar glimmers originating from Nurstin's terrain and decided to explore the phenomenon. A rock-based counterpart to Corthel existed, and it was named Cortheum.