Defensive Harmony

This spell must be cast on at least two creatures. The priest may affect one creature per two levels of his experience, and all creatures to be affected must be within three feet of each other at the time of casting. After the spell is completed, affected characters may move about freely.
Defensive harmony grants affected creatures a defensive bonus by bestowing an enhanced coordination of their attacks and defenses. The affected creatures must be involved in a single battle so that their efforts harmonize to the benefit of all involved. For example, the affected creatures can attack one dragon or a group of orcs in a single area. They can also attack additional enemy forces that arrive in the same combat. If the enemy forces divide and flee, the affected creatures can follow, continue to attack, and benefit from the spell. If the affected group is split into two smaller groups when attacked, however, it gains no benefit from defensive harmony.
While the spell is in effect, each affected creature gains a +1 bonus to armor class for every other creature benefitting from the spell, to a maximum bonus of +5 (although more than five characters may be affected by the spell). Thus, if four creatures are affected by defensive harmony, each creature gains a +3 bonus to armor class.
This bonus represents a mystical coordination of effort on the part of all affected creatures. A fighter will naturally wage his attack to distract the troll attacking the thief. The ranger will instinctively block the swing of an orc, thereby protecting the wizard. Creatures affected by the spell are not consciously aware of these efforts, and they are unable to create specific strategies and tactics.

[Tome of Magic]

Sphere: Law
(Enchantment/Charm)
Level: 4

Range: 5 yards
Components: V, S
Duration: 1 round +2d4 rounds
Casting Time: 1
Area of Effect: One creature/two levels
Saving Throw: None