Fiery Gauntlet

From the Introduction:

Beyond the doors lies a peculiar kind of room. The corridor continues to cross it along it's long axis after a fashion. But instead of walls you find steep drops on either side, with only a few solid columns every few feet. Waves of oppressive heat waft of the molten rock blubbering a few feet below the gangway and its glow plunges the room into a hellish light. Narrow guard platforms line the long walls of the room separated from the central walkway by several feet of glowing molten rock.