The effect of a protection from lightning spell changes depending on who is the recipient of the magic—the caster or some other creature. In either case, the spell lasts no longer than one turn per caster level.
If the spell is cast upon the caster, it confers complete invulnerability to electrical attack such as dragon breath, or magical lightning such as lightning bolt, shocking grasp, storm giant, will 'o wisp, etc., until the spell has absorbed 10 points of electrical damage per level of the caster, at which time the spell is negated.
If the spell is cast upon another creature, it gives a bonus of +4 to the die roll for saving throws made vs. electrical attacks, and it reduces the damage sustained from such attacks by 50%.
The caster's holy symbol is the material component.
Notes: Common for druids (PHB).