You wield two weapons with an artisan’s precision. Each strike builds on the next, allowing you to deal more damage.
Prerequisites: Dex 15, Two-Weapon Fighting, 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 + 1½ 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 two-weapon 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: Player’s Handbook II, page 84. This used to be an epic level feat listed in the Epic Level Handbook (a version 3.0 source updated in part to 3.5 in the Standard Reference Document under Open Game License v1.0a), but as the Player’s Handbook II is the later source, it has precedent, so this feat is no longer epic level.