I went exploring.

I came to a crumbled gap in the base of the tower. I crawled into an unlit interior. My suit’s low-output bioluminescent lamp glowed.

I craned my neck. The bridge rose up vertically above me, a tunnel into the sky. Metal gleamed amid the rubble on the floor.

I kicked aside half-bricks and uncovered a squat cuboid about half my height. It was featureless except for a fat red button. When I pressed the button, the cube rose magically into the air, trailing a rose-colored sparkle, like the bogeys’ weapon; I kept out of the way of the wake. When I released the button, the cube dropped again.

It was pretty obviously a lifting palette.

There was another palette buried in the wall of the bridge—and further up another, and another beyond that.

“Now we know how they made their castles fly,” L’Eesh said. “And how they raised this bridge.” He was standing beside me, his suit glowing green. I saw he had scraped a channel in mold-softened brick with his thumb. Beneath it, something gleamed, copper-brown. “It’s not metal,” he said. “Not even like Xeelee construction material.”

“Maybe that’s the original structure.”

“Yes. No suite of moons is stable enough to allow the building of a brick bridge between them; the slightest tidal deflection would be enough to bring it tumbling down. There must be something more advanced here—perhaps the moons’ orbits are themselves regulated somehow … The bridge itself is just a clumsy shell. The inhabitants must have constructed it after the intervention.”

“What intervention?”

He sighed. “Think, child. Try to understand what you see around you. Imagine millennia of war between the two moons—”

“What was there to fight over?”

“That scarcely ever matters. Perhaps it was just that these were sibling worlds. What rivalry is stronger? Finally, the moons were ruined, serving only as a backdrop for the unending battles—until peacemakers sent down blood-red rays, vacuum energy beams that turned the weapons to dust.”