Aleval School
( Drow of the Underdark, p. 56)[Style]
You have learned House Aleval's fighting techniques, allowing you to deal damage that weakens your enemy's physical or mental state.
Prerequisite
Weapon Finesse (PH) , Spellcraft 2 ranks, Base attack bonus +4, Sneak attack +2d6,
Benefit
When you deal sneak attack or sudden strike damage, you can sacrifice 1d6 points of this extra damage to bestow a —2 penalty on one of the target's three saving throws (your choice) for 1 round.
You can use this feat once per round.