Lightning

Lightning is a demon found in Iris and the Giant.

"The lightning of this demon will make me lose the use of my magical powers for one turn."

Location
In Path of the Giant, Lightning can be found on Floors 14, 18, 19 & 20, and additionally Floors 5B, 6 & 9 on Nightmare difficulty.

In Path of the Ferryman, they can be found on Floors 5, 10 & 12, and additionally Floor 7 on Nightmare difficulty.

They can also be spawned by Pandora's Box in Nightmare difficulty.

Strategy
Lightning will not deal any damage to you, however they will disable the use of any Magical Powers.