Radlight Cap

The radlights caps that flourish in many parts of Nar-Voth look like softly glowing, halfling-sized toadstools: a relatively common sight in the Darklands. When radlight caps change color, however, their dangerous nature becomes evident. With each color change, the fungi gain a new set of stimuli that trigger their deadly spore clouds. While a field of blue mushrooms may have attacked noisy interlopers, when they shift to red they assault anyone who moves a muscle. Many Nar-Voth natives, even non-sentient ones, have learned the colors and corresponding behaviors that will see them safely through a field of radlight caps.

Red Light, Green Light

Ayindilar elves claim that they originally cultivated radlight caps as an advanced warning system against radiation, and that the fungus's other color changes are merely an unintended mutation. Regardless, their original function remains useful enough that the elves rarely eradicate growths of radlight caps. Rather, they teach this warning rhyme to those who must pass through a radlight forest:

Red light stop,
Yellow drop.
Green light rush,
Blue light hush.
Black for terror, black for flight,
For this way comes the sickness light.