Belissan

Found only within the Gates of the Moon, belissan (or moonwood) burns without consumption so long as it remains within that realm, giving off a soft, whitish glow. It is of little benefit outside that area, but to those that often travel the Infinite Staircase, which is considered within the Gates, belissan torches are greatly prized. They can usually be purchased within the Gates of the Moon or from other Staircase travelers for a mere 1 gp apiece.

Reference

• Tales from the Infinite Staircase, pg. 20