Two-Weapon Rend

 
Prerequisite(s): Two Weapon Fighting, Dex 15+, Base Attack Bonus 11+.
 
Benefit: If you successfully hit an opponent with both of the weapons you wield, you deal extra damage equal to 1d6 + 1-1/2 times your Strength bonus. This extra damage is treated as the same type that your off-hand weapon deals normally for the purpose of overcoming damage reduction and other effects related to damage type. You can gain this extra damage once per round against a given opponent.
 
Special: A fighter can select Two-Weapon Rend as one of his fighter bonus feats. A ranger who has chosen the twoweapon combat style can select Two-Weapon Rend as long as he has a base attack bonus of +11 and is wearing light armor or no armor.
 
Source: PHB II