Evocation [Force]
Level: Cleric 3, Paladin 4
Components: V, S, DF
Casting Time: 1 swift action
Range: 0 ft.
Effect: Magic weapon of force
Duration: 1 round
Saving Throw: None
Spell Resistance: No
A spectral weapon composed of pure force energy springs into existence next to you. Each time a foe strikes you, the weapon springs into action, chopping into your foe and dealing a grievous wound.
This spell creates a divine weapon that mimics your deity’s favored weapon. Any time you are struck for damage by a melee attack, this weapon strikes at your foe. It has a base attack bonus equal to your caster level + your Str modifier or Wis modifier (your choice). It deals damage as per your deity’s favored weapon, and is of a size equal to your current size. The weapon gains a bonus on damage rolls equal to 1½ times your Str modifier or Wis modifier (your choice).
There is no limit to the number of attacks that this weapon can make. If a hydra bites at and hits you six times, this weapon in turn strikes at the hydra six times. The weapon has reach or range appropriate to its type. It shares a space with you. If you are Large or larger, it counts as occupying each square of the space you fill.
Source: Player’s Handbook II, page 110.