Santoryu (3.5e Feat)
From D&D Wiki
You have achieved mastery with 3 sword combat.
Prerequisite: BAB+8, Dex 15, Str 13, Three weapon fighting
Benefit: You can now use 3 weapons to a greater effect, the first with -1 penalty, the second with a -2 penalty and the third with a -4 penalty.
Normal: You would take reductions of -2, -5, and -10 respectively
Special: This can be taken as a fighter bonus feat. but only if the character already has Three weapon fighting. When wielding a Light weapon in your offhand and mouth, the penalties decrease to -1 with your main weapon, -1 with your offhand weapon and -2 with the weapon in your mouth.