Keen Edge

Transmutation
Level: Blackguard 3, Paladin 3, Sor/Wiz 3
Components: V, S
Casting Time: 1 standard action
Range: Close (25 ft. + 5 ft./2 levels)
Targets: One weapon or fifty projectiles, all of which must be in contact with each other at the time of casting
Duration: 10 min./level
Saving Throw: Will negates (harmless, object)
Spell Resistance: Yes (harmless, object)
Spell Points: 5

You slide your fingers harmlessly along the edge of the blade, but you know that if someone were to try to repeat the feat, they would be cut bloody with the slightest touch.

This spell makes a weapon magically keen, improving its ability to deal telling blows. This transmutation doubles the threat range of the weapon. A threat range of 20 becomes 19-20, a threat range of 19-20 becomes 17-20, and a threat range of 18-20 becomes 15-20. The spell can be cast only on piercing or slashing weapons. If cast on arrows or crossbow bolts, the keen edge on a particular projectile ends after one use, whether or not the missile strikes its intended target. (Treat shuriken as arrows, rather than as thrown weapons, for the purpose of this spell.)

Multiple effects that increase a weapon’s threat range (such as the keen edge spell and the Improved Critical feat) don’t stack. You can’t cast this spell on a natural weapon, such as a claw.

Augment: If you spend 4 additional spell points, all critical threats scored with a weapon or projectile under the effect of this spell are automatically confirmed (assuming the attack that scored the critical threat hits in the first place).