Greater Multiweapon Fighting( Epic Level Handbook, p. 69)
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.
You may make up to three extra attacks with each extra weapon you wield, albeit at a -10 penalty.
This feat replaces the Greater Two-Weapon Fighting feat (originally presented in Masters of the Wild) for creatures with more than two arms (and functions identically to that feat if you have fewer than three arms).