Kitsunebi

Kitsunebi (Japanese: 狐火 or きつねび, meaning "fox fire") or fox-fire, is named for the magical kitsune who are said to create it. It originates from kitsune and only appears when they are nearby.

This phenomenon is similar to how the Tengu have their own ethereal fire known as Tengubi.

Myths & Legends
Kitsunebi orbs are formed by foxes, which breath the ball of fire out from their mouths and use it to light their way at night. It is most often a sign that a large number of kitsune are nearby – often during yokai events such as the night parade of one hundred demons, yokai wedding ceremonies, and other processions or meetings.

Kitsunebi is not directly dangerous to humans, however the foxes behind it may be. Sometimes it is used to trick humans off of their paths at night. Other times it is used to lure curious humans into the darkness towards a group of hungry yokai. Following kitsunebi usually leads a person to some place that he or she should not be. Additionally, because of its similarity to other dangerous hi-no-tama, it is generally not considered to be a good sign.

Appearance
It appears in large numbers of floating orbs of light, usually only a few centimeters in diameter and less than a meter above the ground. The orbs are as bright as lanterns and in most cases red or orange, or some times blue-green, in color.

Kitsunebi only appears at night, often as a long chain hundreds or thousands of meters long, as if there were lanterns being carried by invisible bearers. Often the kitsune responsible for the fireballs are standing right next to the flames, invisible.