Ninetails (Kyuubi) is a kitsune often referred to as the 'Dark Lord'. However Yami is the true ‘Dark Lord’ and had bestowed her with the title of ‘Lord of Ryoshima Coast’ which is more accurate as it refers to her rule over Oni Island. Ninetails is proud, confident, and holds Yami in the highest respect while viewing all other deities as being "petty" in comparison to her power. The vast majority of Ninetails power lies within an item called the Fox Rods and she is proficient in the use of the Celestial Brush as well as her blade Ninestrike. At her most powerful Ninetails is golden in color with a piñata like fur and white fox mask to conceal her missing eye and scars. At her weakest she resembles a heavily scared red fox with a single tail and no mask.
Ninetails terrorized the people of Ryoshima Coast and the Dragon Palace until the Water Dragon stole the Fox Rods leaving her greatly weakened. She then attended a lecture by the priestess Rao disguised as a ‘fox-faced man’ and waited until they were alone to kill Rao. She took on Rao’s guise and disposed of the body down a well behind Ankoku Temple. When Amaterasu arrived in Sei-an City she tricked the goddess into searching a sunken treasure ship for the Fox Rods and abandoned Amaterasu believing the Water Dragon would finish her off. Amaterasu later retrieved the Fox Rods from the Water Dragon’s belly and still fooled by Ninetails guise willing handed them over believing they were a holy artifact.
Queen Himiko is later found dead in her Palace killed by Ninetails who reveals her true form and challenges Amaterasu hoping to be rid of the goddess once and for all. Frustrated by the small size of the room which limited her maneuverability Ninetails retreated to Oni Island to rally her dark forces where she hid in a constellation and created a nine-tailed shadow on the moon in mockery of Amaterasu's patterns on the sun. Confronted again by Amaterasu and surprised that the "foolish beast" had made it so far the two fought once more and with Ninetails demise Oni Island collapsed into flowers almost as if a "funerary offering" to it’s fallen master.
"9 souls inhabit 9 tails, each acting independently. Burning the tails will temporarily weaken it, and a lightning strike to the sword causes the souls to split apart." -Bestiary
In Japanese mythology a kyūbi no kitsune (nine-tailed fox) is a malicious, multi-tailed, shape-shifting fox usually associated with the elements of fire and lightning. They are easy to anger and quick to avenge. Similar trickster fox spirits include the Chinese húli jīng (fox spirit) and the Korean kumiho (nine-tailed fox).
Ninetail's actions are similar to the legend of Tamamo-no-Mae.