Monks that follow the Way of the Infinite Abyss channel their ki into more demonic practices, focusing on controlling the chaotic energy in the world, and drawing it out in other beings. They are likely to have made some sort of contact with a demon or fiend that has opened their eyes to the way of the abyss. These monks may serve as guards or servants of a temple dedicated to a greater fiendish power, or carry out the will of some demonic entity on their own accord. Those who wish to follow this monastic tradition most closely will seek out chaos in the world, and stoke the flames to the best of their ability.

Demonic Detriment

When you choose this subclass at 3rd level, you gain access to the effects of certain spells, as well as the thaumaturgy cantrip. As an action, instead of dealing damage when using your unarmed strike, you can spend 2 Ki points to inflict the effects of Bane, Command, Crown of Madness, Hex, or Hold Person. You can spend 2 more Ki points to attempt to affect another creature within melee range as a bonus action immediately following your action. The saving throw DC for the effects of your spells uses the same save DC as your Ki save.

Strike of the Demon

At 6th level, you can gain a pool of energy equal to your monk level that you can disperse as a bonus action upon a successful melee strike on an enemy. You can choose how much of this energy pool is expended to add to a damage roll. This damage can be any of the following types: Fire, Cold, Lightning, Necrotic, or Poison. You can spend any number of available Ki Points to add to this damage, at a value of 1 ki point per extra point of damage. You regain the full pool of energy back upon a long rest.

Fiendish Force

At 11th level, your ability to channel the effects of chaos expands. As an action, you can spend 4 Ki Points to cast Banishment, Contact other Plane, Dominate Person, Dominate Beast, or Fire Shield. For any ability that requires the target to make a saving throw, you must first make a melee attack using your unarmed strike bonus.

Soul of the Demon

At 17th level, you can use your action to magically assume the form of a demon once per long rest. Your form turns into that of any fiend (demon) of a challenge rating of 10 or less. You can maintain this form for a number of hours equal to half of your Wisdom modifier rounded down with a minimum of 1 (if your Wisdom modifier is +1, your transformation lasts for half an hour). You automatically revert back to your original form if you fall unconscious, drop to 0 hit points, or die.You can also revert back to your original form as a bonus action. When transformed, the following rules apply:

• Your game statistics are replaced by that of the demon, but you retain your alignment, personality, and Intelligence, Wisdom, and Charisma scores.
• When you transform, you assume the demon’s hit points and Hit Dice. When you revert back to your normal form, you return to the number of hit points you had before you transformed. However, if you revert as a result of dropping to 0 hit points, any excess damage carries over to your normal form.
• You can only speak in the languages the languages your normal form is capable of speaking, unless the demon is not capable of communicating verbally.
• You do not have access to any of your regular monk abilities while in the demonic form.

After exiting the demonic form, if you are still conscious, make a Wisdom saving throw. If you roll less than a 10, the demonic powers cloud your mind, and you enter a furious and chaotic rage. Your next turn must be spent attacking whatever creature is closest to you as if it is a life threatening enemy. This bloodlust lasts until you deal damage to said creature, or you are knocked unconscious. If the creature dies before you can injure it, or moves at least 300 ft. away from you, your focus shifts towards whatever creature is now closest to you.