Whoever fights monsters should see to it that in the process he does not become a monster" but the way I see it, only a monster can kill another monster. Monks who follow the teachings of the Corrupted Vessel believe that only by becoming a monster can you defeat a monster. They subject themselves to a dangerous metamorphic ritual that leaves their body’s mangled and mutated, many do not survive the process. By infusing their body’s with fiendish blood they then train to manipulate the mutations granted by the process of infusion with their Ki. 

Corrupted Mutation

At 3rd level, The fiendish blood within you can be manipulated by your Ki to mutate your flesh and make you more adaptable in battle.

As a bonus action you can spend 1 ki point to activate one of the following mutations. These mutations last for one minute, you activate another mutation, become incapacitated, or die.

Bone Spurs. Sharp bone like protrusions tear through your flesh and cover your body. Whenever a creature hits you with a malee attack they take piercing damage equal to one roll of your martial arts dice.

Flesh Tendrils. You  grow two fleshy tendrils alongside your arms. As an action, you can use one of them to grapple a creature. Each one is also a natural weapon, which you can use to make an unarmed strike with. If you hit, they do bludgeoning, slashing, or piercing  damage equal to one roll of your martial arts dice + your strength or dexterity modifier. Immediately after hitting, you can try to grapple the target as a bonus action. These tendrils are not dexterous enough to use weapons, magic weapons, and other specialized equipment.

Warping Reach. Your arms twist and elongate in unnatural ways. You gain an extended reach of up to 5ft.

 

 

Aspect of Corruption

The fiendish blood within you leaves visible signs of Corruption. Choose 2 effects from the Aspect of Corruption table or determine it randomly.

Aspect of Corruption
d6	Aspect of Corruption
1	Your eyes, nose, and mouth bleed while using an ability
2	Illusory shadow figures surround you while you take a short or long rest.
3	You faintly smell of rot, decay, sulfur, or any other putrid smell.
4	You are affected by the Levitate spell while sleeping during a short or long rest.
5	Horns sprout from your head or small spikes protruded from your body.
6	Your skin and hair color change to more sinister colors.

 

 

 

 

 

Corrupted Comprehension

Additionally at 3rd level, you learn one of the following languages: Abyssal or Infernal.

 

In addition, you gain proficiency in Intimidation. 

Corrupted Implements

at 6th level, you learn to use your Ki to manipulate the power of the fiendish blood inside of you. A Corrupted implement requires you to spend ki points each time you use it.

 

You know the Fiend Tracker Implement and one other Corrupted Implement of your choice. You learn one additional corrupted Implement of your choice at 6th, 11th, and 17th level.

 

Whenever you learn a new Corrupted Implement, you can also replace one Corrupted Implement that you already know with a different Implement.

 

By spending 2 Ki points (unless stated otherwise) you can as an action, activate the fiendish blood in your body to grant you one of the following effects. These effects last for the duration or until you use another corrupted Implement effect. The effects end early if you become incapacitated or die.

Bone Chilling Expansion

By spending 3 ki points, as an action Your body warps, twists, and swells unnaturally. Your size doubles in all dimensions, and its weight is multiplied by eight. This growth increases your size by one category - from Medium to Large, for example. If there isn't enough room for you to double your size, you attain the maximum possible size in the space available. Until the effect ends your flurry of blows deal an extra martial arts dice of damage, you also have advantage on Strength Checks and Strength Saving Throws. This effect lasts for 1 minute.

Dark Water

As an action you can spend 2 ki points to sprout gills and warped webbed appendages, you gain a swim speed of equal to your walking speed and can breathe underwater. This effect lasts for an hour.

Demonic Distortion

By spending 3 ki point, as an action Your body becomes blurred, shifting and distorting to all who can see you. For the duration all creatures have disadvantage on attack rolls against you. An attacker is immune to this effect if it doesn’t rely on sight, as with blindsight, or can see through illusions, as with truesight. This effect lasts for 1 minute.

Devilish Eye

By spending 2 ki points, As an action Your eyes turn black as coal. For the duration, you have dark vision out to 60 ft. In addition you can see in magical darkness, This effect last for 4 hours.

Fiend tracker

you can use your action and expend one Ki point to focus your awareness on the region around you. For 1 minute per number of Ki points you expend, you can sense whether a fiend is within 1 mile of you per Ki point spent.

Malleable Grasp

The bones in you arm begins to feel loose and malleable. Spend 2 ki points, as an action You can attempt to grab a creature or object within 15 feet of you and pull them closer or pull yourself self closer to them. The creature must succeed on a strength saving throw against your Ki save Dc or be pulled towards you 15ft. The creature can be 1 size larger or smaller then you.

The Watcher

As an action you can spend 1 ki points. Eyes envelope your dominant arm giving you advantage on perception checks that deal with sight. This effect lasts for an hour.

Thick Hide

As an action You can spend 1 ki points as Your flesh starts to tear and harden into a tough scaled texture. You gain a +2 to your AC. This effect last for an hour.

Twisted Ascension

As an action you can spend 2 ki points to gain the ability to move up, down, and across vertical surfaces and upside down along ceilings, while leaving your hands free. You also gains a climbing speed equal to your walking speed. This effect lasts for an hour.

Resistant Reaction

Starting at 11th level, as a reaction you can spend 1 Ki points when you are hit by an attack dealing acid, cold, fire, lightning, or thunder damage to momentarily gain resistance to that damage type.

Fiendish Fury

Starting at 17th level, you have complete control over the flesh warping ability of the fiendish blood within you. By spending 4 Ki points, as an action Twisted, fleshy, tendril like appendages sprout from your body. Each creature in a 15-foot-radius sphere centered on you must make a Dexterity saving throw against your Ki save dc. A target takes 8d6 bludgeoning, piercing, or slashing damage on a failed save, plus an extra 1d6 damage for each additional ki point you spend. On a successful save, the creatures take half as much damage.This attack is considered magic for purpose of overcoming resistance and immunity to nonmagical attacks and damage.