Kensai

Martial Archetype
Comments from the Finger: This is a class was originally written by The Palm, and has since been revised by me. Essentially, this 3.5 class was a class that focused on making your signature weapon have extremely high modifiers, and was a favorite for min-makers because these modifiers could be translated into weapon properties, like burning or vorpal. We've distilled that down into a fighter that becomes very proficient in hitting things with a single weapon. That being said, I think this class channels the Samurai aesthetic better than most, and places it rightfully in the fighter category.

     Frankly, I have my doubts about the balance of the final two class features of this class, which I've messed with pretty extensively and have yet to find a retool I'm completely happy with. Of course, fighter archetypes are somewhat difficult to gauge the power of, simply because of the power gap in the core fighter subclasses, particularly with how weak the Champion is compared to the Eldritch Knight.

Kensai

The archetypical Kensai is an honorable swordsman, possessing great power and mastery over her single chosen weapon. An expert in controlling her life energies, a Kensai imbues her chosen weapon with her own Chi and bonds to it, allowing her to wield it with greater finesse than a normal warrior.

Extension of Body

Beginning when you choose this archetype at 3rd level, you may attune to a weapon that you are proficient with by meditating for 24 hours. By imbuing a weapon with your own Chi, the weapon forms a special link with you and becomes your signature weapon. You may only have a single signature weapon at a time. It is now considered a magical weapon which grants a +1 bonus to attack rolls. Additionally, if you can see your weapon and it is within 30 feet, you may have your signature weapon fly to your hand as a bonus action. If you try to make an attack with any weapon other than your signature weapon, you may not apply your proficiency bonus to attacks.

Extension of Soul

At 7th level you learn to extend your Chi to affect others. You gain advantage on Charisma (Persuasion) and Charisma (Deception) checks while you are within 5ft of your signature weapon if you are proficient in these skills. After using this ability to gain advantage on a roll, you cannot use it again until you complete a short or long rest.

Extension of Blade

At 10th level, through countless battles and days of maintenance, you have gained the ability to wield your weapon with precise control. You may now apply an additional half your proficiency bonus (rounded down) to attack rolls using your signature weapon.

Power Surge

At 15th level as a bonus action, you can channel your Chi to guide your blade. While wielding your signature weapon, you may double your proficiency bonus to attack rolls and add your proficiency bonus to damage with your signature weapon for the rest of the round. After using this ability, you cannot use it again until you complete a short or long rest.

Extension of Mind

At 18th level, you can impart a shard of your consciousness into your signature weapon as a 1 hour ritual requiring concentration and grant it sentience for 1 day. While your signature weapon has sentience, by closing your eyes and concentrating on your weapon as an action, you can enter a Zen State for one minute. Until you lose concentration or choose to end the Zen State as a bonus action, you have blindsight with a range of 30 feet and cannot use your normal sight.  You move at half speed and cannot be surprised.  While in a Zen state, you may not attack normally, though you can launch a single precise attack each round. As an action, you may make a single weapon attack with advantage using your signature weapon. If this attack hits, you may add your total attack bonus as damage to your damage roll. You may not use Power Surge if you are in a Zen State. After you enter a Zen state, you may not enter it again until you complete a long rest.