As soon as the Adamantium door closed completely, the cramped staircase they were walking down was plunged into darkness. Both Jake and Carmin switched to night vision and four luminous globes, including a pair of glittering galaxies and another of crimson stars, pierced the night.
With their hypersensitive eyes, the staircase before them looked as bright as day. Even without any secondary source of light, Jake could easily emit a brief light pulse, whose photons would be partially reflected by the surfaces illuminated by it.
It was similar to the echolocation method used by bats to find their way around. Of course, he could light up these dungeons for good, but turning the light back on suddenly would not help their so far furtive approach.
