Random Causality

This spell creates a rift in the nature of cause and effect. The spell is cast upon an opponent's weapon. When the weapon is used, it hits and causes damage normally, but the damage is not applied to the creature struck by the weapon. Instead, the person wielding the weapon or one of his companions suffers the damage. If the weapon misses its target on any round, no damage is caused in that round.
Using a die roll, the DM randomly determines the victim of the damage. The DM selects a die with a value nearest the number of eligible creatures (the wielder of the weapon and his companions). If the number of creatures does not equate to highest value of a die, the wielder of the enchanted weapon takes the extra chances to be hit.
For example, if a goblin wields a sword affected by this spell. he and his six companions are eligible to receive the damage. The DM rolls 1d8. On a roll of 1-6, one of the goblin's companions suffers the damage; on a roll of 7 or 8, the goblin with the affected weapon suffers the damage. The weapon is affected for 3 rounds + 1 round/ level of the spell caster. If the wielder of the weapon changes weapons while the spell is in effect, the discarded weapon remains enchanted.

[Tome of Magic]

Sphere: Chaos
(Alteration)
Level: 3

Range: 10 yards
Components: V, S, M
Duration: Special
Casting Time: 3 rounds + 1 round/level
Area of Effect: One weapon
Saving Throw: Negates

Material Components:
a bronze die