Goryoushin

Goryoushin (ゴリュウシン, "Goryuushin") is a type of Oni in the Shaman King series.

About
A Goryoushin is a type of Shikigami created by local Onmyōjis to protect the capital against evil spirits. They are independent Over Souls and have a finite amount of Furyoku that made them disappear once depleted.

During battles, they fight with all their might and quickly use their Furyoku reserves. As such they would have to be replaced periodically.