Moon o' War
A hostile, floating jellyfish that senses movement in the air and drains light from nearby travelers.
Drifts in place on the still air of the cave, all but blind. It senses only movement in the air close to it; stay still or pass slowly at a distance and it never wakes. Stir the air too near it and it turns, creeping slowly toward the disturbance; let it reach you and it latches on to suck your stored light energy.
This moonborn creature is shaped like a man o' war, bobbing through the lightless Jellyfish Cave on currents only it can feel. Eyeless and slow, it reads the world as ripples in the air; the faster and nearer you move, the louder you are to it. Disturb one and it drifts your way, deliberate and unhurried, until it is close enough to fasten on and drain the light from your reserves.