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The main cavern of the Elk Raiders' home is what remains of a large lava tube. Aeons ago, lava cooled across the bottom, making the tube semi-circular. Into the mountain, the tube extends. At a quarter-mile underground, the tube pitches gradually downward, ending a mile deep at a spring of hot sulfurous water. Somewhere far beneath, the water meets magma, sending scalding steam up through the water. The original pool was too hot for bathing and too sulfurous for drinking. A member of the Elk Raiders constructed a nearby pool that, with proper management, was just right for bathing. Nearer the exit, where the lava tube vomited half-digested rock onto open ground, the vent collapsed in cooling, closing the mouth. With a few changes, the Elk Raiders made the entrance highly defensible, now
