A creature with three or more hands can fight with a weapon in each hand. The creature can make up to three attacks per round with each extra weapon.
Prerequisites: Dex 19, three or more arms, Improved Multiweapon Fighting, Multiweapon Fighting, base attack bonus +15.
Benefit: The creature may make up to three extra attacks with each extra offhand weapon it wields, albeit at a –10 penalty on the third attack with each weapon.
Special: This feat replaces the Greater Two-Weapon Fighting feat for creatures with more than two arms. A ranger who meets only the base attack bonus prerequisite and the Improved Multiweapon Fighting prerequisite can gain this feat, but can only use it when wearing light armor or no armor. A fighter can select Greater Multiweapon Fighting as one of his fighter bonus feats.
Source: Standard Reference Document under Open Game License v1.0a, which updated this feat originally published in the Epic Level Handbook, page 69.