Spirit of Fire

The Spirit of Fire (スピリット・オブ・ファイア, Supiritto Obu Faia) is one of the Five Grand Elemental Spirits (Godaiseirei), that are said to be created by the Great Spirit itself. It is primarily associated with Asakura Hao.

About
The Spirit of Fire is one of five powerful elemental spirits known as the Godaiseirei. They are derived from the Great Spirit itself, and like it, constitute a collective of souls. They can be controlled by their respective Elemental Warrior, or a shaman of extraordinary power (like Asakura Hao). The power of the Godaiseirei is unmatched by any other spirit, except for maybe the Great Spirit itself.

The Spirit of Fire has the ability to consume other souls and spirits in order to further enhance its own power. Its primary medium for its over soul is the element of air, which allows Hao to manifest the Spirit of Fire with incredible speed. However, it also has the ability to transform itself into the different five elements through the doctrine of the five phases, which is made possible through Asakura Hao's mastery of the elements.

Past
500 years before the start of the series, Hao was reincarnated as a member of the Patch tribe, the organizers of the Shaman Fight. Although he would fail to become the Shaman King, he succeeded in stealing the Spirit of Fire from the tribe, using it as his guardian ghost when he once again reincarnated 500 years later. In its adult and most powerful stage, the Spirit of Fire is gigantic, with a muscular body, broad shoulders, black claws and black lava rock armor down its legs.

Present Time
Its power was greatly diminished because of its journey back from Hell (where Hao negotiates the terms of his reincarnations with Taizan Fukun, the god of the dead), forcing it to regain its strength by consuming other souls. Together, Hao and the Spirit of Fire were an unstoppable force that was all but destined to win the Shaman Fight.

In the manga, Hao discards the Spirit of Fire after the other competitors forfeit the Shaman Fight, making Hao the Shaman King and the inheritor of the Great Spirits. The Spirit of Fire then became the spirit ally of Lyserg Diethel, its destined Elemental Warrior. It was transported to Lyserg and the others by Redseb Munzer, who had been killed by Hao along with Seyram Munzer. It was later seen being kept inside an Corn Silo and overlooked by Kalim of the Ten Patch Officiants, and later somehow made it's way inside the Great Spirit together with Lyserg.

O.S. "Spirit of Fire"
O.S. "Spirit of Fire" (O.S.スピリット オブ ファイヤ)
 * Shaman: Asakura Hao; Lyserg Diethel
 * O.S. Type: Spirit Type
 * Spirit Ally: Spirit of Fire
 * Medium used: Oxygen in the air

Description: This is Hao's primary oversoul. He manifests the Spirit of Fire, one of the five great spirits of nature, onto the physical plane by integrating it with the oxygen in the atmosphere. Using onmyōdō magic, Hao can alter the nature of the Spirit of Fire into any of the five elements (fire, water, wood, metal, and earth).

Attacks
 * Magma Upper (マグマ アッパー, Maguma Appa): An attack where the Spirit of Fire stretches it's arm forwards and showers the opponent in Magma, with a temperature exceeding 1200°C.
 * Volcano (火山, Kazan): Lyserg launches a large amount of fire into the air as a defensive move.

O.S. "Spirit of Fire: Black Fowl"
O.S. "Spirit of Fire: Kurobina" (O.S.スピリット オブ ファイヤ:黒雛)
 * Shaman: Asakura Hao
 * O.S. Type: Armor Type
 * Spirit Ally: The Spirit of Fire
 * Medium used: Oxygen in the air

Description: This is Hao's armor type oversoul, which transforms the Spirit of Fire into jet armor. With it, Hao is capable of high-speed flight, and can attack swiftly with the oversoul's arms. Mounted on the back are two energy cannons, which can incinerate anything it targets within seconds. As with most armor type oversouls, this form requires little of Hao's furyoku, but consumes a considerable amount of the Spirit of Fire's reiyoku. However, it offers capabilities which far surpasses that of O.S. Spirit of Fire.

Attacks
 * Onibi: An attack that blasts the opponent with the two cannons on Hao's back. This attack is strong enough to destroy the archangel Azazel, an angel whose reiyoku level was higher than that of the Spirit of Fire.

Anime/Manga Difference
In the anime, Hao would ultimately deem the Shaman Fight to be a pointless contest, and would move to acquire the Great Spirits by force. After fighting through various obstacles, the Spirit of Fire would seemingly consume the Great Spirit itself, being reborn in a golden hue ten times its previous size. With their new found power, Hao and the Spirit of Fire would defeat any and all challengers except for Asakura Yoh, who would defeat the duo with the combined might of every shaman, friend, and ally present.

Also during his short fight with Yoh, Hao displayed the ability the reform the Spirit of Fire into a sword similar to Yoh's Spirit of Sword.

Trivia

 * The Spirit of Fire has a vague resemblance to an airplane.