Gravity globe

A gravity globe, or grav globe, was a human device to provide massive illumination. It could be sent aloft under its own power so that it would "hang" at a certain height and provide light over a large area. Grav globes were particularly useful in large caves.

Ida Scott used a globe to light up Krop Tor's core. (DW: The Impossible Planet, The Satan Pit)

The Clerics used a globe to light up the Maze of the Dead. (DW: The Time of Angels, Flesh and Stone)