King clipped a stop descender onto the line. Its squeeze trigger would allow him to slow his descent by loosening his grip. The counterintuitive function of the device was hard to get used to, but once mastered, it worked without flaw. Of course, that was when rappelling down a cliff face feetfirst. King was descending a vertical stone pipe—head first. He wrapped his feet around the line to keep himself from flipping over and slid into the tunnel. Hidden from the light of day, he reached up and pulled his night vision goggles over his eyes.

The tunnel shot straight down as far as he could see. With wiggle room on either side and a clear shot down, King squeezed his stop descender and plummeted down the hole. The others followed, one by one, spacing out their drops every twenty seconds.

The air grew warmer as King dropped down the pit. And the light ahead grew brighter; so much so that he had to reach up and remove his night vision goggles. Something was down there, he just hoped he wouldn’t find himself dangling above a pit of lava, or a firing squad.

As King approached the bottom of the hole he eased up on his grip and began slowing. The yellow tip of the line’s end was thirty feet below. If he didn’t stop by the time he reached it, he’d fall to the floor below.

Before he expected, King was out of the vent, dangling over a large orb-shaped room. He quickly scanned the space for danger; finding none, he zipped down the line to the stone floor. The others followed him quickly, leaving their descenders clipped to the dangling line. Should anyone find it, their presence would be detected. But they weren’t planning on remaining covert for much longer.

As King approached the room’s only exit and a tall hallway beyond, he saw the light source ahead and paused. A sphere of light, the size of a small plum, floated eight feet above the floor. There was no bulb that he could see and no line dropping down to the light.

Alexander joined him. “This is very bad.”

They entered the room slowly, unable to take their eyes off the light. King motioned to Bishop and Knight. “Take point.” As the pair moved to the far end of the hallway, King stopped beneath the light. He held his bare hand up to it. The heat was searing up close, but dissipated quickly. He shook his head in amazement. This small sphere was lighting and heating several large rooms beneath a mountain.

Queen crouched next to him and picked up a handful of sand from the hallway floor.

“What are you doing?” King whispered as she stood.

“When you got close to it, your hair stood on end,” she replied.

“A static charge?”