Santoryuu (4e Feat)
From D&D Wiki
You have learnt santoryu, the three-sword style.
Prerequisite: Fighter, 11th level, Two-Weapon Fighting
Benefit: If you are wielding a shortsword in each hand, you can also wield a shortsword in your mouth. If you do so, the two-weapon fighting damage bonus for your primary weapon increases to +2. You may treat it as your off-hand weapon for the purpose of attacks, drawing and sheathing.
Special: You may not speak whilst wielding a weapon in your mouth.