Aosagibi

The Aosagibi is a yokai from the swamps, marshes and wetlands of Japaland, and appear as a normal blue heron, but it has an ability; turning itself into a blue fireball, well not actually a fireball, but can be seen on fire. They were first described in 811 A.D, as one sighting, but have also turned into an illustration phenomenon, with more sightings going on.

Origins
Folklore built around the phenomenon tells a story of an old blue heron transforming into a yokai. The herons' feathers fuse into shining scales that give off an iridescent blue light in the dark of night. The yokai's breath is also said to release golden powder into the air that collects to form a heat-less fiery light, though this light eventually dissipates in the wind. The harmless creature is said to flee from human contact, retaining a normal heron's shyness

Length
About the length of a normal blue heron

Diet
Bugs, worms and fish.

Country
Japaland

Physical Characteristics
Many birds transform into magical yokai with eerie powers when they reach an advanced age. Aosagibi is the name for a bizarre phenomenon caused by transformed herons – particularly the blue heron. Other herons and wild birds, such as peafowls and pheasants, are able to develop this ability as well, though it is most commonly attributed to the nocturnal night heron. This heron is found all along the islands and coasts, preferring remote areas with heavy reeds and thick woods. Aosagibi is most commonly seen at night in the trees where the herons roost, by the rivers where they hunt, or as the birds fly in the twilight sky.