Spirit of Power

This cooperative spell is rarely used or spoken of, since its requirements are strict and the outcome is uncertain. The spell must be cast by six priests of the same faith. All six must touch hands at the time of casting. At the completion of the spell, the priests fall into a trance. The life essences of the priests leave their bodies and merge at a point within 10 feet of the casters. The spirits of the priests meld together to form the avatar of the priests' deity.
In this manner, the six characters become a single being with all the powers and abilities allowed to that avatar. The only stipulation is that the priests' deity cannot have created all avatars allowed to it at that moment. If this has happened, the spell fails and the priests are drained as described below.
If the spell succeeds, the priests have completely given their wills over to their deity, essentially forming the vessel into which it funnels power. In becoming the avatar, the priests retain the ability to make most of their own decisions. (The six must work in harmony or allow one of their number to decide all actions.) However, the deity can assume direct control of the avatar at any time it desires — the avatar is, after all, an earthly manifestation of the deity.
Although the spell has a duration of one hour, the deity is not obliged to release the priests at that time. If the priests are not released at the end of the spell's duration, they instantly die. A deity can choose to sacrifice its priests in order to maintain its avatar on the Prime Material plane. Such a cruel and unjust action is almost never undertaken by good deities or those that have any respect for life, free will, or mercy. For dark and sinister gods, the question is much more uncertain, If a deity chooses to maintain the avatar longer than one hour, control of the avatar instantly and permanently passes to the DM. (Clearly, a DM should seldom if ever exercise this power.)
While the priests are formed into the avatar, their bodies remain in a death like trance. The priests have no idea what might be happening to their real bodies (unless the avatar can observe them). Any damage to a priest's body requires an instant system shock roll. If successful, the damage is recorded normally, but the damage does not take effect until the spell ends (at which point the priest will almost certainly die). If the system shock roll is failed, the character instantly dies and the spell ends. Characters who die in this manner cannot be Raised, Resurrected, or reincarnated. They have been taken to the ultimate reward (or punishment) for the service they have rendered. If the bodies are moved from their positions, the spell ends.
Even if the deity releases the priests, they are left severely drained. All spells memorized are lost until the priest can rest and perform his prayers once again. The physical drain leaves each priest with only 1 hit point upon awakening, regardless of the number of hit points the character had when the spell was cast. Since damage suffered during the spell takes effect instantly, any priest who is hurt dies immediately (although quick action by others might save him).
Each priest who survives the spell will be bound by a Quest (a duty that must be completed in exchange for calling upon their god).
The material component is an offering appropriate to the deity. The DM determines the exact nature of this offering.

[Tome of Magic]

Sphere: Summoning
(Summoning, Invocation)
Level: 7
Cooperative

Range: 0
Components: V, S, M
Duration: 1 hour
Casting Time: 3 turns
Area of Effect: The casters
Saving Throw: None

Material Components:
an offering appropriate to the deity