As a monk you can study the Way of the Hellish Flame. With this subclass you embody the vengeful spirit within yourself. Taking inspiration from the devils that walk the planes. Turning their ferocity into a tamable essence. Focusing their hellfire into yourself. The teaching of this tradition is emulating devils in order to further attach your soul to the material plane and its magic. By altering yourself to resonate with devilish might, you augment your prowess with raging hellfire to bolster yourself even going so far as burning your mortal flesh. Be wary, however, the very devils you learn from may decide to whisper half truths and tricks into your ear. Or maybe you could find yourself corrupting yourself by the end.

Demonic Disciple

When you choose this tradition at 3rd level, you learn to mimic the speech and mannerisms of devils, granting you the following benefits.

• You learn to speak, read, and write infernal.
• You gain proficiency in intimidation if you are not already proficient.
• You gain darkvision with a range of 60 feet.

Kyton's Grasp

You gain a natural weapon that takes on the appearance of a blade affixed to a long chain, which you can use to make unarmed strikes. This natural weapon has the reach property and counts as a monk weapon for you. You are proficient with it, and you add your Dexterity modifier to its attack and damage rolls. Its damage is piercing, and its damage die is a d4. This die changes as you gain monk levels, as shown in the Martial Arts column of the Monk table.

 

Additionally, you can expend 1 ki point to extend the range of this natural weapon for a single attack. The range of the attack becomes 20 feet and if you deal damage to a creature with the attack you can force them to make a contested strength check. If the target fails, they are pulled up to 10 feet toward you.

Hellish Visage

As a bonus action, you can expend 2 ki points to adopt your visage, gaining the following benefits until you choose to end the effect or until 10 minutes have passed.

 

• The first time on each of your turns that you hit a creature and deal damage to it, you can deal an additional 1d6 fire damage to the creature.
• Fire damage dealt as a result of Hellish Visage and any of its benefits ignore resistance to fire damage
• You gain resistance to fire damage.

In addition to the previous benefits, when you activate Hellish Visage you choose one of the following benefits to gain for the duration.  Some benefits require you to be of a certain monk level. Beginning at 9th level you may take two benefits rather than one.

Demon Dash. Whenever you use the Step of the Wind ki feature, you gain the ability to freely move through spaces occupied by other creatures, but you still cannot end your turn in another creature’s space. Any creature whose space you pass through must make a Dexterity saving throw, taking damage equal to one roll of your Martial Arts die, or half that damage on a success. Once a creature takes damage from this feature they cannot take damage from it again until the start of your next turn..

Hellport. Upon taking damage you can, as a reaction, expend 2 ki points to teleport to an unoccupied space you can see within 50 feet. Any creature within 10 feet of either the space you leave or the space you arrive in (your choice) must make a Dexterity saving throw or take fire damage equal to two of your Martial Arts dice.

Demonic Fury. Once per turn, you may forgo one of your melee attacks and expend a ki point to cast Fire Bolt in place of the attack. Wisdom is your spellcasting modifier for this spell and it scales based on your monk level. 

Hellish Defense. Whenever you use the Patient Defense ki feature, any creature who attempts to make a melee attack against you before the start of your next turn must additionally make a Dexterity saving throw or take fire damage equal to one roll of your Martial Arts die.

Devil’s Reflection. Whenever you use the Deflect Missiles feature to reduce the damage of an incoming attack you may reduce the damage by an additional amount of d10’s equal to your half proficiency bonus (rounded up). If the damage is reduced to 0 and you expend a ki point to make the ranged attack specified by the feature, you can increase the damage by an additional 1d8 fire damage.

Fallen Ashes. When you use the Stunning Strike feature while Hellish Visage is active, if the creature fails the Constitution saving throw, the creature is also set aflame. The fire lasts for the duration of your Hellish Visage or until that creature or another creature takes a turn to douse the fire. The target takes fire damage equal to one of your martial dice at the start of each of the creature's turn.  

Brutality. Whenever you reduce a creature to 0 hit points, creatures of your choice within 30 feet that can see you must make a Wisdom saving throw. On a failed save the creature immediately uses its reaction, if available, to move as far as its speed allows away from you. The creature doesn’t move into obviously dangerous ground, such as fire or a pit. A blinded creature automatically succeeds on the save. You must be a 9th level monk to choose this benefit.

Haunted Spear. When you hit a creature with an attack using Kyton’s Grasp, you can expend 1 ki point to make another attack roll against another creature within 10 feet of the original target. You must be an 11th level monk to choose this benefit.

Fatality

At 11th level you gain the ability to empower your strikes by inflicting pain. After hitting a creature with two consecutive melee attacks, the next successful attack against that creature made before the end of your turn is treated as if it were a natural 20.

 

Once you use this feature, you can’t use it again until you finish a short or long rest.

Unending Rancor

At 17th level you have become one with your demonic powers, allowing you to effortlessly assume your visage. You no longer need to expend ki points to activate Hellish Visage. 

Your Hellish Visage also gains the following benefits in addition to the benefits already granted by the feature.

• Fire damage dealt as a result of Hellish Visage and any of its benefits deal half damage to targets with fire damage immunity.
• You gain immunity to fire damage while Hellish Visage is active.