Your manipulation of ki focuses on drawing life energy from other creatures. Much like the school of Necromancy, this way of practice is frowned upon by most orders. However, there are still some who dare practice this art, and worse...use it.

Withering Strikes

When you choose this tradition at 3rd level, you begin to be able to draw out life from creatures you strike. Once per turn, when you hit a creature with an unarmed strike, you may mark them as withering for up to a minute. A withering creature takes 1d4-1 necrotic damage (minimum of 1) at the end of each of its turns. A Lesser Restoration ends this effect early. Undead and Constructs are immune to this feature. The damage increases to 1d4 at 5th level, 1d4+1 at 11th level, and 1d4+2 at 17th level.

Aura of Decay

Starting when you choose this tradition at 3rd level, as an action you may spend 2 ki points to create a 10 foot radius of decay around you. Any creature that ends its turn in this aura takes damage equal to the damage caused by your Withering Strikes. A withering creature who ends its turn in the aura takes additional damage equal to your Wisdom modifier + your Proficiency bonus. You may expend additional ki points to extend the aura by 5 feet for each additional ki point spent.

Dark Ki Shroud

When you reach 6th level, you gain resistance to necrotic damage. Whenever you reduce a creature to 0 hit points, you may gain a number of temporary hit points equal to your monk level.

Cursed Touch

At 11th level, once per turn when you hit a withering creature with an unarmed strike you may choose one of the following effects

• The creature takes twice as much damage from your Withering Strikes feature
• The creature becomes poisoned until the end of its next turn
• You may spend 1 ki point to cast Bane on the creature
• You may spend 3 ki points to make the creature vulnerable to the next attack that hits it
• You may spend 5 ki points to cast Blight on the creature

This feature may affect only one creature at a time. 

Withered Soul

At 17th level, you master the art of drawing the life from a creature's ki. At the start of combat, you may inflict withering on one creature you can see within 60 feet. When a creature takes damage from your Withering Strikes feature, you gain a number of hit points equal to half the damage dealt.