Monks of the Way of the Reaper are obsessed with the meaning and mechanics of dying. Whether they capture foes and set elaborate traps to isolate their subjects and find out what death really means, or whether they were reborn and brought to life from undeath. Brought up in the slums where death bears its disgusting head every corner you look. These monks have channelled the very meaning of murder, and now yield it's fighting style.

Deathly Nature

Your almost blood -lined bond between you and death affects you in multiple ways, some good. Some bad:
You gain Resistance to necrotic damage. (Necrotic damage cannot reduce you to 0 hit points)
You gain vulnerability to radiant damage. (When you are reduced to 0 hit points by radiant damage, you can't use 'friend of the grave')

Life Steal

Starting when you choose this tradition at 3rd level, your study of death allows you to extract vitality from another creature as it nears its demise. When you reduce a creature to 0 hit points, you gain temporary hit points equal to your Wisdom modifier + your monk level (minimum of 1 temporary hit point).

Reaping Touch

As you bring a creature close to its death you exploit its diminishing life energy, once a creature is below half of its maximum hit points, you can deal and extra martial arts die of damage when you hit it with an unarmed strike. (This can only be used once per turn).

Hour Of Despair

At 6th level, you gain the ability to unsettle or terrify those around you as a bonus action. When you do this, each creature within 30 feet of you that can see you must succeed on a Wisdom saving throw (DC 8 + proficiency bonus + wisdom mod) or be frightened of you until the end of your next turn. 

Friend Of The Grave

Beginning at 11th level, you use your familiarity with death to escape its grasp. When you are reduced to 0 hit points, you can expend 1 ki point (no action required) to fall to 1 hit point instead. 

Additionally you can spend 2 ki points to roll your monk hit die (d8) and fall to that hp instead.

Soul Rend

Starting at 17th level, you've mastered the grave and control the very vital signs of creatures around you, as an action you can spend ki points to affect the hp of target creatures of your choosing within 30 ft, if the amount of hp affected exceeds and/or is equal to the current hp of the chosen creature(s). They die.

1 ki point = 10 hp