Monks of the Way of Kensai have a different relationship with weapons than other warriors do. While many see them merely as tools to be used, a Kensai comes to recognize that they have a spirit of their own, A Kensai seeks to enter into a relationship with the weapon, to understand it, and through understanding form a fearsome partnership. Kensai do not enchant the weapons, they have no magical talent themselves. Instead, through deep meditation and reflection, they can draw deeply hidden and latent powers and properties out of a weapon.

Whisper to the blade

Beginning at 3rd level,. the Kensai begins to hear and understand the words of weapons. At the end of a short or long rest, you gain a deep awareness of the spiritual nature of one weapon of your choice. This weapon becomes known to you. You gain proficiency with the known weapon, and it is considered a monk weapon. You may apply either your Strength or Dexterity modifier to your attack and damage rolls with the weapon. Additionally, the weapon counts as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage. Beginning at 8th level, you can add your Wisdom modifier to all damage rolls made with your known weapon.

This awareness lasts until your next short or long rest.

Language of Steel

While a weapon is known to you, you are proficient in the creation of that weapon. You can craft such a weapon in either half the usual time or at half the usual cost.

Additionally, you can help others better understand the deep language of steel and wood. At the end of a long rest, of which at least one hour is spent in discussion with an ally, you grant that ally a single weapon proficiency. This proficiency lasts until the ally's next long rest. If they are already proficient with the weapon, they instead gain an additional +1 bonus to attack and damage rolls with it. This effect stacks with any magical properties the weapon may have. You need not be proficient in the weapon yourself to grant this ability

Speak to the Soul

Beginning at 6th level, you can draw mystical properties out of your known weapon, awakening it's latent energies. By spending ki points you can produce the following effects:

 

Stoke the Soul. You can spend 2 ki points to bring the weapon alive with elemental properties. Choose one element: acid, cold, fire, lightning, or thunder. For the duration of your deep awareness, the weapon yields a soft light and adds an additional 1d6 of the appropriate damage type. After this imbuement is completed, you can spend an additional ki point, up to 3 ki, to increase this elemental damage by 1d6 for each ki point spent, lasting for one round. This effect stacks with any magical properties of the weapon. Only one element may be applied at a time

Sharpen the Soul. The weapon more eagerly seeks your foes. You can spend 2 ki points to give the weapon a +1 bonus to attack and damage rolls. You can spend up to 6 ki points this way. This effect stacks with any magical properties of the weapon.

Fortify the Soul. The weapon moves more quickly to intercept attacks from your foes. You can spend 2 ki points to grant you a +1 bonus to AC. You can spend up to 6 ki points this way. This effect stacks with any magical properties of the weapon.

While each effect must be paid for separately the effects do stack, and last until your next short or long rest. For example, a Flaming (2), sharpened +2 (4), Fortified +3 (6) attunement would cost 12 ki points.

Two Speaking as One

Beginning at 11th level, you can reproduce the soul of your weapon on the material plane. Once per short rest, you can summon a spiritual weapon, as per the spell, as a bonus action. However, the spiritual weapon is an exact, if spiritual, version of your known weapon at the time, including any Speak to the Soul abilities you have imbued into it. You can make one attack with it as a bonus action on each of your turns, and it uses your Wisdom for attack and damage bonuses.

Additionally, you have advantage on saving throws to resist the effects of sentient or cursed weapons.

Unleash the Roar

Beginning at the 17th level, your Spiritual Weapon no longer requires a bonus action for you to activate. When you take the attack action, the spiritual weapon can also make one attack. Additionally, when you use your Flurry of Blows, the extra unarmed attacks can be replaced with known weapon attacks instead.