To cast this spell, the priest must be in sight of a rainbow, or have a special component (see below). The rainbow spell has two applications, and the priest can choose the desired one at the time of casting. These applications are as follows: Bow: The spell creates a shimmering, multi-layered short composite bow of rainbow hues. It is light and easy to pull, so that any character can use it without penalty for nonproficiency.
It is magical: Each of its shimmering missiles is the equivalent of a +2 weapon, including attack and damage bonuses. Magic resistance can negate the effect of any missile fired from the bow. The bow fires seven missiles before disappearing. It can be fired up to four times per round. Each time a missile is fired, one hue leaves the bow, corresponding to the color of arrow that is released. Each color of arrow has the ability to cause double damage to certain creatures, as follows: Red—fire dwellers/users and fire elementals Orange—creatures or constructs of clay, sand, earth, stone or similar materials, and earth elementals Yellow—vegetable opponents (including fungus creatures, shambling mounds, treants, etc.) Green—aquatic creatures, electricity-using creatures, and air elementals Indigo—acid-using or poison-using creatures Violet—metallic or regenerating creatures When the bow is drawn, an arrow of the appropriate color magically appears, nocked and ready. If no color is requested, or a color that has already been used is asked for, then the next arrow (in the order of the spectrum) appears.
Bridge: The caster causes the rainbow to form a seven-hued bridge up to 3 feet wide per level of the caster. It must be at least 20 feet long and can be as long as 120 yards, according to the caster's desire. It lasts as long as the spell's duration or until ordered out of existence by the caster.
The components for this spell are the priest's holy symbol and a vial of holy water. If no rainbow is in the vicinity, the caster can substitute a diamond of not less than 1,000 gp value, specially prepared with bless and prayer spells while in sight of a rainbow. The holy water and diamond disappear when the spell is cast.