Way of the Flagellant

The Way of the Flagellant use pain as a means to center themselves, regain purity, and to help others. They are strongest when they can weaken themselves. When they are closer to death, they are stronger but have a more limited toolkit. 

Shared Punishment

Starting when you choose this tradition at 3rd level, you can injure yourself in order to spread the suffering to enemies. As a bonus action on your turn, you can choose to use a weapon to hurt yourself, dealing a number of d8 damage of the weapon's type. Every creature of your choice within 30 feet of you that you can see must succeed a Constitution saving throw, taking the same number of d6 slashing damage on a failed save, or half as much on a successful one.

Undying Body

At 6th level, you gain the ability to delay death. When you are reduced to 0 hit points but not killed outright. you can spend any number of ki points. You can roll a number of d8 equal to the ki points spent, distributing the total value as hit points across up to five creatures within 60 feet of you that you can see. You can heal yourself with this, and can only use this feature once every long rest.

Lash's Anger

When you reach 3rd level, you learn to channel your pain into your attacks. Once per turn when you are below half your maximum hit points and roll damage for your attack, you can choose to deal 1d8 necrotic damage. This damage increases to 2d8 at 6th level, and 3d8 at 11th level.

Transference of Pain

Starting at 11th level, you can shield others from harm at the cost of your own health. When a creature within 30 feet of you takes damage, you can use your reaction to magically take that damage, instead of that creature taking it. This feature doesn't transfer any other effects that might accompany the damage, and this damage can't be reduced in any way.

Exsanguinate

At 17th level, you gain the ability to wreath your body in a shield of blood. You can use your action to spend 6 ki points and target an enemy creature within 30 feet that you can see. That creature must make a Constitution saving throw. On a failed save, the creature takes 12d8 force damage or half as much on a successful save. You receive temporary hit points equal to half the damage you deal. If you are below half health, the creature has disadvantage on the saving throw.