Path of the Santroyu Swordsman

Those who persue the way of three swords do so for one reason, and one reason alone: to be the best swordsman in the world. The unorthodox methods they use quickly attract fame, should they survive to enjoy it. A santoryu swordsman may enjoy the pain he inflicts in others, may desire the strength to protect those he loves, but no matter his motivation, he loves fighting. 

Santoryu Ogi (Three Sword Style)

Starting at 3rd level, you have made the first step to truly master the art of the blade, as it was never been seen before.

You have learned the basics of the 3-sword-style, in which you use a sword with your teeth, but it must be a light weapon and all weapons must be swords. If you are equpit with 3 sword in that way, you can use your bonus action to attack with your off hand and your weapon in your mouth, but all attack are with disadvantage.

Your abilities with your third sword will improve on further levels. Starting at level 6, you now can use other swords with you mouth, ass long as it doesn't have the heavy and/or two-weapon property. Starting at level 10, you can now add you strength modifier to your sword at your mouth. Starting at level 14, you have finally masterd the 3-sword-fighting-style and you don't get disadvante for attacking with 3 swords.

You also learn the two-weapon fighting style (which let you use your Str. Mod to you second weapon, but not to you weapon at your mouth).

Oni Giri (Demon Cutter)

Starting at level 6, if you use the dash action and at least moved half the movement in a streight line, you can make 1 attack roll and if that attack hits, you roll the damage, as if you did hit the enemy with every weapon you have equipt (this does also include critical hits). You can use this featue a number of this equal of you babarian level devided by 3.

Hyakuhachi Pound Ho (108 pound canon)

Starting at level 10 you now know a special attack, in which you can attack from a distance. In a 120 feet range you can attack a enemy in sight with the combiened strike of you 3 swords. The target must make a dexterity saving throw (DC = 8 + proficiency modifier + strength modifier). If the target fails, it takes 3d8 force damage, but if they succed, they take no damage. If the target has at least half cover or if it's prone, it gets advantage on the saving throw.

Asura Form

Starting at level 14, if you use a bonus action to rage, you can spend a second use of rage to take the asura form.

In this asura form, you form through an illusion a total of three left arms, three right arms and three heads. Each copie of the arms and the head has the same weapons as the original. In this form, you can attack 6 times with an action and 3 times with an bonus action to a total of 9 times. You can't grapple or shove someone in this form. This form last for 1 minute or dismiss it as a free action, in which you are losing your rage (this form can't be extended by persistent rage) and have to use another use of rage, if you want to rage. You can use this ability, you must finish a long rest before you can use this ability again.