Way of the Hollow

Ki is the natural life-force that flows through all living things. While most monks learn to harness Ki in a beneficial way, that naturally strengthens their body, those who pursue the way of the hollow have learned to use it in more dreadful ways. While they still maintain the practice of using Ki to increase their health, they also use it in a way that hollows them out from the inside, damaging them in ways that bring them closer, and closer to death.

Revitalizing Ki

Starting at 3rd level, you have the ability to heal yourself with Ki points. At the start of your turn, for no action, you can spend as many Ki points as you wish to heal. For each Ki point you spend, you regain 4 + your Constitution modifier Ki points (to a maximum of 7). You cannot use this feature while you are incapacitated.

At higher levels: At level 6, this ability increases to 5 + your Constitution modifier (to a maximum of 8). At level 11, this maximum is increased to 9, and at level 17, it is increased to 10.

Damaging Lifeforce

At 6th level, you gain the ability to add your hit dice to your unarmed strikes. When you use Flurry of Blows, you can expend 2 hit dice without healing, and do an extra 1d8 necrotic damage with each of your two bonus action unarmed strikes (The hit dice are expended before you hit or miss the target).

Alternatively, if you are making a single unarmed strike as a bonus action, you can expend a hit dice to add 1d8 necrotic damage to that unarmed strike (Like the previous option, this hit dice is expended before you hit or miss the target).

Hollowing punch

Beginning at 11th level, you can deal damage to yourself to increase your damage output against others. Whenever you use an action to hit a creature with an unarmed strike, you can necrotic damage equal to a roll of your martial arts die to both you and the target creature. Whenever you do this, you gain a number of temporary hit points equal to the damage you received (if you already have temporary hit points, you can choose to not receive these ones).

Additionally, when using your Damaging Lifeforce feature, you can choose to receive the additional 1d8 necrotic damage in place of expending a hit dice (you must decide this before rolling your attack rolls). Whenever you do this, you gain a number of temporary hit points equal to the damage you received (if you choose).

Balance of death

At 17th level, you gain the ability to fail a death save for more Ki points. Using a bonus action, you can fail 1 or 2 death saves to regain 5 Ki points per each death save (this is done while you are conscious, and above 0 hit points). When you fail a death save in this way, these death saves remain failed until you take a long rest, and cannot be undone in any way until then.

Additionally at level 17, you gain the ability to spend Ki points on resistance or immunity to necrotic damage. Upon rolling initiative, you can spend 4 Ki points to gain resistance to necrotic damage, or spend 8 Ki points to gain immunity to necrotic damage.

At higher levels: At level 18, when you use your Empty Body class feature to turn invisible for 1 minute, you can also spend an additional 4 Ki points to gain immunity to necrotic damage for that minute.