Multiweapon Fighting( Monster Compendium: Monsters of Faerûn, p. 9)
A creature with three or more hands can fight with a weapon in each hand. The creature can make one extra attack each round with each extra weapon.
Three or more hands,
Penalties for fighting with multiple weapons are reduced by 2.
This feat replaces the Two-Weapon Fighting feat for creatures with more than two arms. The Multidexterity feat further reduces penalties for off-hand attacks.
A creature without this feat suffers a -6 penalty on attacks made with its primary hand and a -10 penalty on attacks made with its off hands. (It has one primary hand; all the others are off hands.) See Attacking with Two Weapons in Chapter 8 of the Player's Handbook.