Dragon

“That’s the mountain.  The prison itself is nicknamed the Birdcage because it is suspended in the center of the empty mountain, hanging only by the same network of tubes that supplies prisoners and food to the cell blocks.  Both the interior of the tubes and the interior of the mountain itself are vacuums.  Even if an individual were to have powers allowing them to navigate the vacuum, I have three thousand antigrav drones in position at any given time, laying dormant in that lightless void, waiting for any signal, motion, energy or air leakage to awaken them.  Once awakened, a drone will move to the location of said anomaly and detonate.  Many of my drones contain a loadout of containment foam, but others contain payloads designed to counteract various methods one could theoretically use to traverse the vacuum.  Some are quite lethal.”

Interlude 6