You psionically make a weapon keen, improving its ability to deal telling blows. This 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 power can be manifested only on piercing or slashing weapons. If used on arrows or crossbow bolts, the effect 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 power.

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