Nyths are creatures very similar to will-o'-wisps and the two species can communicate and have been known to ally with each other. Nyths are often mistaken for wisps but some northern barbarians can supposedly tell the two apart, naming nyths "wildfire" and thinking them to be evil spirits. Nyths have a slightly wider range of colouration than wisps.
Nyths do not feed on negative emotions as wisps do but instead eat their prey like most predators. They have a natural ability to shoot magic missiles from their bodies and, while they can extinguish their glow like a wisp (but only for a short time and not if they fire a missile which causes their body to glow even brighter), they prefer to hide in the light of the sun.
Nyths reproduce by absorbing fire or lightning energy. Such energy heals a nyth and when a certain amount of that energy is absorbed, a nyth splits into two separate creatures. This process causes an explosion of light and sends a multitude of magic missiles flying in random directions. The Nyth's affinity with magic missiles goes even further, they are immune to damage from missiles cast at them by other creatures and also reflect them back at whoever manifested them. Nyths are also immune to any effect that influences the minds of creatures due to their completely alien thought processes and are completely silent unless speaking.
Nyths are sometimes recruited as guardians and take great pride in defending their homes against specified intruders.
People have learned to avoid nyths as nyths will avoid them in turn but in 1367 DR during the Rat Hills Conflagration, guard patrols from Waterdeep spotted a group of will-o'-wisps and nyths and engaged them. The fire caused the nyths to reproduce exponentially and the explosions of magic missiles killed two of the Waterdhavians. As of 1372 DR there was believed to be four nyths still in the Rat Hills but many, many more in Ardeep Forest.