ItemPropertyDecreaseSkill

From NWN2Wiki

// Returns Item property decrease skill.  You must specify the constant for the
// skill to be decreased(SKILL_*) and the amount of the penalty.  The penalty
// must be a POSITIVE integer between 1 and 10 (ie. 1 = -1).
itemproperty ItemPropertyDecreaseSkill(int nSkill, int nPenalty);