Spirit of the Tree of Ages

 is the very essence of the Sacred Tree of Ages itself from both timelines. It had remained dormant for the entire anime of InuYasha.

History
During the events from when Kikyō pinned Inuyasha to the sacred tree, the spiritual energy within the arrow tip was infused with the priestess's essence. The said essence was absorbed by the tree, enabling it to take on the appearance and voice of Kikyō.

Yashahime
The spirit made its first appearance in The Gateway to the Past where it was watching over a sleeping woman in the core of the tree, detecting the arrival of the half-demon princesses. The spirit asked the girls a request to slay the Beast King Kirinmaru.

Personality
Being infinitely wise and knowledgeable, it also seems to have acquired a bit of Lady Kikyō's personality as it has taken on her form to commune with Sesshōmaru, and his twin daughters and niece.

Physical Description
It has no known form but has since borrowed the form and voice the late priestess Kikyō.

Relationships
To be added

Media Appearances

 * Episode 4 (Hanyō no Yashahime)
 * Episode 8 (Hanyō no Yashahime) (dream)
 * Episode 17 (Hanyō no Yashahime)
 * Episode 18 (Hanyō no Yashahime)

Trivia

 * In the Avatar franchise, there is the ancient Tree of Time of the Spirit World, where the very first Avatar, Wan, had permanently merged with the mighty Spirit of Light and Peace, Raava, who was then transformed into the Avatar Spirit. Avatar Wan had then imprisoned the Spirit of Darkness and Chaos, Vaatu, inside its hollow for the next ten millennium. The Tree of Time remembers everything in existence.
 * Despite its wisdom, the spirit seems to get some facts mixed up, or possibly distorts the truth. Kirinmaru at present is content with his territory, with Zero being the only real threat; though it's likely Zero will be slain by the half-demon princesses and causes Kirinmaru to embark of the idea of warping time.