Head back towards the pulsing room

You can't stop thinking about the glowing room back the way you came, and it draws your attention more than continuing forward does- you wanted to make sure it was nothing before continuing. Returning back the way you came proves to be a bit of a trek, as you slowly find your way back up the small hill that you came down. When you reach the top, you find yourself in a wide cavern, a broad dome in shape, with the floor and ceiling littered with the rock formations of stalactites and stalagmites. The strange glow fills the room, seeming as if it originates in the very center. Tall, impassible stone walls line the sides, as the entrance you just came through appears to be the only break within sight.

You decide to head towards the center of the room, rather curious as to the source of the glow. It's not easy going, as the rocks on the ground are difficult to find proper footing in the dim light. Steadily growing brighter as you approach the center of the room, the dim glow is an odd off-white color that leaves a strange green tint on the rocks. Within several minutes, you reach the source of the light, as there's a strangely even, disturbingly circular space that is devoid of stalagmites. Even the dirt on the ground appears to form a spiral, centering in on a small, smooth rock, which is glowing with the only light in the room.

Looking in at the center in particular, it appears to simply be a small pebble, one that would easily fit in the palm of your hand. It's emitting a dull glow, not nearly bright enough to hurt your eyes looking at but plenty bright enough to illuminate the cavern, casting long shadows on the distant walls. Perhaps the strangest part is that it appears perfectly smooth, but the surface of the rock almost seems to pulse and shift with the light.