Two-Weapon Fighting, Perfect (Feat)

Prerequisites: Level 21, BAB +16, Dex 25, Two-Weapon Fighting, Greater (Feat), Two-Weapon Fighting, Improved (Feat), Two-Weapon Fighting (Feat)

Benefit: You gain a fourth attack with your off-hand weapon, at -5 to hit. This gives you two -5 to-hit attacks with your off hand.

Normal: Your fourth attack with a given hand is made at -15 to-hit. But this is an Epic Feat, and is just that good.