From D&D Wiki
|This material is published under the OGL 1.0a.
Multiweapon Fighting [General]
Dex 13, three or more hands.
Penalties for fighting with multiple weapons are reduced by 2 with the primary hand and reduced by 6 with off hands.
A creature without this feat takes 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, and all the others are off hands.) See Two-Weapon Fighting.