Way of the Cursed Fist

Monsters that stalk the night, hungry for blood, preying on the weak. Creatures from other realms whose minds are set on conquering the worlds of man. Demons from the blazing pits of hell that strike tainted deals in blood. To hunt and kill these creatures can often require more than just a trained hand. Sometimes, to hunt a monster, one must become a monster. Monks of the Cursed Fist understand this idea and take it as a fact more than a metaphor. Through the use of ancient blood magic they capture and bind the souls of devils to their own in order to harness their power.

When you pick this tradition select a CR20 or lower fiend. This fiends soul is now bound to yours. This will become relevant as you gain more levels in the subclass.

Note For DMs and Players 

This monk tradition operates in very similar ways to a warlock. The demon you've captured and bound to your soul should have a personality of its own. There should be some kind of dynamic between the pc and this creature. As the player you should work with your DM to create the personality of this demon. Are they constantly plotting escape, attempting to screw you over, or anything else like this should be discussed and implemented how you and the DM see fit.

 

Twinned Soul Strike

Starting when you choose this tradition at 3rd level you gain the ability to touch a targets soul rather than their physical body. When you hit a creature with an unarmed strike you may expend a ki point to preform a Twinned Soul Strike. Rather than take damage from the hit they become gain the soul struck condition. The target gains additional stacks of this condition every time they are hit by this ability. This condition lasts until you finish a short or long rest. 

As a reaction you may choose a target that has the soul struck condition and expend all stacks. For each stack of Soul Struck the target takes damage as if it had just been hit by your unarmed strike without expending ki points. In addition you may apply any on hit effects as if you had just hit the target. This reaction interrupts whatever triggered it. IE: forcing a stunning strike in reaction to a party member getting hit to prevent them from being hit or to push the target out of range/knock them prone. 

Twin Soul

Starting when you take this tradition at 3rd level you gain the ability to tap into the power of your bound demon. You gain a marking somewhere on your body that symbolizes the connection to this demon. Whenever a creature uses any ability that allows them to detect the location or presence of fiends they pick up on you as well as any other fiends in the area. In addition any spell that affects fiends affects you as if you were a fiend.

As a bonus action you may expend a ki point to do one of the following.

• You allow the demon a brief moment of control. You make your next ability check with the demon's stats rather than your own.
• You draw on the demons vitality. Heal yourself equal to one roll of your demons hit die. 
• You harness the power of your demon seal to fortify your resolve. Delay damage from one attack for the next 1d4+constitution modifier rounds. This effect must be used in reaction to being hit and may be used after damage is rolled but, before damage is applied. 

Imperfect Possession

Beginning at 6th level your mastery and control over your soul bound demon have increased to the point you can fend off its mental influence while tapping into more of its power. You can make use of your deflect missile feature against any ranged spell attack that targets only you.

In addition you may expend 2 ki points as a bonus action to allow the demon to partially possess your body. Half of your body becomes covered in strange black markings and you gain the following for 1 minute.

• You gain Temp hp equal to 2x your monk level.
• The first strike you make after activating this ability may be treated as a twin soul strike without expending a ki point
• You're Twin Soul Strikes deal bonus damage equal to your charisma modifier

When your imperfect possession ends you gain 1 level of exhaustion.

Soul Merger

Beginning at 11th level, your soul has begun merging with the soul of your demon. You gain any condition immunities your demon has. Any damage immunities your demon possesses become resistances for you. You reduce damage you would take from damage types your demon is resistant to by an amount equal to your wisdom modifier. 

Perfect Possession

At 17th level, you gain the ability to allow your demon to take control of your body without fear of losing control. As a bonus action you may expend 5 ki points to activate your cursed form for 1 minute. While active you gain the following benefits.

• You increase your hit point maximum by 2x your monk level.
• You gain all damage resistances and immunities your demon has. 
• You may choose to use your demons armor class in place of your own.
• When you use your flurry of blows feature you may expend 2 additional ki points to use it 1 more time. These additional hits automatically count as Twined Soul Strikes.
• Your hit points cannot drop below 1 hp.

After using this feature you gain 1 level of exhaustion. Once you use this feature you must complete a long rest before you may use it again.