Vexing Miscalculation

Enchantment (Compulsion) [mind-affecting]
Level: Artificer * 2, Cleric */Oracle * 2, Inquisitor * 2, Warlock * 2
Components: V, S
Casting Time: 1 Standard Action
Range: close (25 ft. + 5 ft./2 levels)
Target: one creature
Duration: 1 minute/level or until discharged
Saving Throw: Will negates
Spell Resistance: yes
  You frustrate an opponent with ill fortune that leads even its most accurate attacks astray. The target is unable to score critical threats for the duration of this spell, even if the result of its roll would normally be a critical threat. If the creature rolls a natural 20, the attack still hits regardless of its opponent's AC, but the hit is not eligible for a critical confirmation roll. Once a critical threat has been foiled by vexing miscalculation, the spell is discharged.