This Ancient spirit was once one of the Dead Race.
Hood Episode Three
This entity watches the Hunter throughout his journey through the forest. The spirit randomly appears in flashes. Its motivation is unknown. Does it intend harm or no?
Hood Episode Four
The Ancient spirit welcomes the Hunter to Gorsus, or the Spirit World. The spirit reveals it was trying to help guide the Hunter on his quest to find Cameron. The Ancient spirit needs the Fenrirr's help. The spirit reveals that long ago when it was alive, it was one of the group entrusted with the recapture of the extremely dangerous demon who now has control of Cameron. The spirit's group was successful in capturing the demon, but they were attacked by some unknown powerful enemy. The demon escaped. As the spirit's group tracked it again, the demon killed them one by one. The Ancient spirit was the last to die. Now, this spirit and the lost spirits of its companions are trapped in the Spirit World. If the Hunter kills the demon, the Ancient spirit and its fellows will finally be free.
Once the Archdemon is dead, the Ancient spirit and his fellows disappear from the Spirit World.