You practice the fighting style of Warding Crescent. This fighting style draws power from the moon to guard you against attacks and wait for the right opportunity to strike quickly and precisely. This subclass is designed around tanking as many hits as possible and retaliating when the time is right. Also, you can only gain the benefits of this subclass if you wield a weapon with the finesse trait or a longsword.

Sword Training

At level 3, you gain proficiency in martial weapons with the finesse trait and longswords. These weapons count as Monk Weapons for you. You can use your dexterity for attack and damage rolls with longswords.

Moonlight Ward

Starting at level 3, you can summon a pool of protective moonlight around you to protect you from harm. As a bonus action, you can spend a number of Ki points up to your Wisdom modifier (minimum of 1) to create a Moonlight Ward. The Ward is a circle centered on you with a radius of 10 feet. It shines dim light and moves with you. If a creature of your choice or yourself takes damage in the ward's area, they only take half damage (rounded down). The other half of the damage will be absorbed by the ward. The ward has a number of hit points=(1 roll of your martail arts die+your consitution modifier)*the number of Ki points you spent. This feature does not work on Psychic damages.

When the ward is dropped to 0 hit points, it will shatter but not disappear. It will regain hit points if you use Ki points to fuel a Monk feature that deals damage. The hit points regained is equal to 2*the Ki points you spent.

Once you use this feature, you cannot use it again until finishing a long rest.

Crescent Blade Techniques

Starting at level 6, when you have your ward active, the moonlight infused with your blade can punish your opponents for daring to attack you or your allies with the following Crescent Blade Techniques:

The Blazing Moon: When an enemy enters the area of your ward on its turn, you can make an attack of opportunity against them. If you spen 1 Ki point on this feature, the attack will crit on a 19 as well as a 20 and the Critical Hit will deal thrice the damage instead of twice.

The Evening Moon: When an enemy damages you or your allies in the ward, you can use your reaction to reduce the damage by 1 roll of your Martial Arts Die+your Wisdom Modifier. If you spend 1 Ki Point, your can make an attack of opportunity against a hostile creature in your ward as part of the same reaction, dealing an extra damage equal to the damage you absorbed with this feature.

The Hazy Moon: You infuse your weapons and ward with Ki to strengthen them. As a bonus action, you spend Ki points up to your proficiency bonus. The ward's radius increases by 5 feet for every Ki point spent until the start of your next turn. When an enemy enters the area of your ward on their turn or starts their turn there, you can use your reaction to force them to make a dexterity saving throw. If they fail, they will take 3*your martial arts die of radiant damage. If they succeed, they will only take half damage.

If the opportunity attacks from Evening Moon and Blazing Moon hits, your speed and the target's speed will be both reduced to 0.

Unsheath the Moon

At level 11, your ward empowers you further. When the ward is active, you can use your bonus action to use 2 Ki points so that your weapons will extra damage equal to your proficiency bonus for 1 minute. After you used this feature, you can't use it again until you finish a short or long rest.

Also, when you make an attack of opportunity, you can spend 1 Ki point to make two attacks instead of one.

Improved Moonlight Ward

At level 17, you have mastered your Moonlight Ward. You and all creatures of your choice in the ward will have half cover. In addition, you can now move freely after using your Crescent Blade Techniques.