Three Sword Style

You have mastered a very strange art of combat, the Three Sword Style, where you wield a sword in each hand, and one in your mouth. This practice is most likely created by you and only you, or it could be an ancient technique passed down from generation to generation. Either way, this ridiculous style of sword fighting is a unique and not well known art that looks insane but is powerful in it's own right.

Third Hand

Beginning at 3rd level, you can wield a weapon in your mouth allowing you to attack more than you normally could,  but leaving you with a slight disadvantage. While wielding three swords you can make two attacks with your bonus action instead of the normal one as per the two weapon fighting rules, this additional attack follows all other rules and limitations associated with normal Two-Weapon fighting.

Tri-Wielder

Also at 3rd level, the Dual-Wielder feat is affected and changed because of your strange fighting style. When wielding three swords simultaneously you gain an additional +1 to your armor class and can draw your third weapon as a bonus action. All other bonuses granted by the Dual-Wielder feat and/or fighting style apply to Three-Weapon Fighting.

Sharpening the Senses

At 7th level, If you know the enemy and know yourself you need not fear the results of a hundred battles. As a part of either a long or short rest you may meditate instead of doing other activities. If you do so you gain the benefits of the rest, and you may make any Wisdom check or Saving throw with advantage until your next rest.

Additionally, you gain proficiency with Wisdom saving throws.

Flying Slash

Starting at 10th level, your training of swift attacks has allowed your normal swordsmanship to truly shine with a single devastating attack faster than the eye can see. As a part of the Dash action on your turn you can make a single attack while moving, you must move through an enemies square to perform this move and while moving through his square the enemy cannot make attacks of opportunity against you. You make an attack roll against that creature with advantage, and if the attack hits it is considered a critical hit.

You can use this feature once per long rest, regaining expended uses on a long rest.

Six-Armed Demon

At 15th level, your mastery over your Three Sword Style and your speed of attacks has given you the appearance of a six-armed demon in the battlefield. As an action on your turn you may select a target within 30 feet of you, that target must make a Wisdom saving throw (DC = 8 + Proficiency Modifier + Wisdom) or become frightened of you until the end of your next turn. You can use this feature again after a long rest.

While a creature is frightened of you you may make 2 additional attacks against it as the after image of your attacks fused with your spiritual energy creates additional swords and arms to attack your foes.

Perfect Swordsmanship

Finally, at 18th level, you have finally perfected the art of the Three Sword Style. You gain one additional attack as a part of your bonus action. Additionally you may, once per long rest, caste haste on yourself as an action, as you fully unleash your speed and ferocity.