Monks trained in the way of the needle use a variety of Ki infused abilities to enhance both their melee strikes as well as ranged attacks made with darts, commonly reflavored as Senbon a small metal needle used commonly as a thrown weapon.

Those who follow this path could be trained assassins who wander the land seeking out targets to eliminate with deadly precision leaving unseen wounds. Or perhaps they are simply the protectors of the monastery of which they call home. 

Members of this way are usually mysterious, and find comfort remaining unseen. many of whom protect their true identity from those around them to not be associated with the actions of others. 

Piercing Hand

Starting when you choose this tradition at 3rd level, You learn to focus Ki into your fingertips. Doing so allows you to make more pinpoint strikes against your opponents. Whenever you make an unnarmed attack you may choose to deal piercing damage instead of bludgeoning. 

Needles

You learn to empower your darts with Ki, upon choosing this tradition at 3rd level Darts act as monk weapons for you, and their damage scales with your martial arts die.

Additionally when you make a ranged attack with a dart you may spend 1 ki point to roll an extra martial arts die per ki point spent when calculating damage.

The number of Ki points available to spend for this ability increases to 2 at 6th level and again to 3 at 11th level. 

Adept Throw

At 6th level, you are able to infuse more Ki into your darts. When making a ranged attack with a thrown weapon, you no longer make the attack roll at disadvantage due to a creature being in melee range, and your attacks ignore 1/2 and 3/4 cover.

Hidden Attacker

By 11th level, your movements and attack have quickened and become more precise. You gain proficiency in the stealth skill. if you already have proficiency you gain expertise instead. 

Additionally piercing attacks made by you now leave no visible wounds.

Dart Barrage

Upon reaching level 11 in this subclass, the Ki added to your Darts also gives them the magical property if they lacked it. 

You also gain the ability to replace your unnarmed attacks made with flurry of blows with thrown weapon attacks using darts. Additionally when you use flurry of blows you may make one additional ranged attack against a creature of your choosing using a dart.

Thousand Needles

At 17th level, you can bring about a barrage of needles. When you hit a creature with an attack roll you may spend 1-5 Ki points and have the target make a Dexterity saving through with a DC equal to your spellcasting DC. This ability deals magical piercing damage equal to your martial arts die 2 times for each Ki point spent and restrains the creature. On a succesful save the creature takes half damage and is not restrained (spending 3 Ki points for this ability will deal damage equal to 6 martial arts die). When this ability is used a barrage of spectral needles appear around the target shooting through them from various directions. 

Once this feature is used it cannot be used again until you finish a long rest.