Many monks achieve perfection of the body through use of martial arts and self-discipline, but for those that follow the Way of the Hollowed Soul this is only partially true. Those who walk this path do so by channeling the dark energy of the Fel and using it to enhance their natural capabilities. While the Fel grants its wielders great power, enhanced speed, and durability, it also saps the very life-force from those around them. Monks of the Hollowed Soul are forever tainted by their connection to the Fel, often times finding themselves succumbing its destructive nature even in situations where it would be unreasonable. This duality ultimately causes irrevocable havoc upon the wielder's state of mind, who must regularly fight their darker urges, lest the Fel consume them entirely.

Fiendish Regeneration

When you choose this path at 3rd level, your newfound ties to the Fel grants you the ability to heal at a remarkable rate. You may spend one ki point as a bonus action to heal a number of hit points equal to your Monk level plus your WIS modifier. In addition, you are resistant to Necrotic damage.

At level 10, this healing can repair even grievous injuries. If you lose a body part, this healing causes the missing part to regrow and return to full functionality after 1d20 + 4 hours if you have at least 1 hit point the whole time.

Fiendish Form

Starting at 6th level, you can spend 2 ki points as a bonus action to tap into your reservoir of Fel energy, granting you unmatched power, durability, and reflexes for 1 minute. Ki points spent on this ability can only be recovered by finishing a long rest. While in this form your eyes and veins pulse with the eerie glow of Fel energy, and wispy tendrils of smoke exude from your body. You may choose to end the transformation at any time as a free action. You gain the following benefits while this ability is active:

• Your melee attacks deal an additional die of necrotic damage. You heal a number of hit points equal to half the necrotic damage dealt by each attack, rounded up.
• Your AC increases by your Constitution modifier.
• You have advantage on Dexterity based ability checks and saving throws.
• If an opponent misses you with a melee attack, you may use your reaction to immediately make an attack of opportunity against them.

Dark Miasma

By 11th level your ties to the Fel have greatly improved, enhancing your Fiendish Form. While active, your body now takes on a wraith-like appearance, and the tendrils of smoke now coalesce into a dark miasma that permeates 30 ft. around you. Any creatures that move into the cloud or start their turn within it must make a CON save, taking necrotic damage equal to your Monk level + your WIS modifier on a failed save, or half as much on a successful one. You heal a number of hit points equal to half of the damage taken by this effect, rounded up. In addition, you gain access to the following new technique:

• Siphoning Blast. You can spend 4 ki points as an action to unleash a powerful blast of Fel energy. This blast deals 5d10 necrotic damage to all creatures in a 30 ft cone or half as much on a successful CON saving throw. You heal a number of hit points equal to half the damage taken by this ability, rounded up. You may only use this technique while your Fiendish Form is active.

Fel Wraith

At 17th level, your connection to the Fel has reached its apex. You no longer have to spend Ki points to activate your Fiendish Form and can maintain it indefinitely. While active, you now gain a Fly speed equal to your normal movement and become incorporeal. You can move through other creatures and objects as if they were difficult terrain, however you take 1d10 force damage if you end your turn inside an object. You become immune to non-magical forms of damage, and resistant to all magical damage. In addition, you gain access to the following new technique:

• Raise Specter. You may spend 4 Ki points as an action to target a humanoid within 10 feet of you that has been dead for no longer than 1 minute and died within your miasma cloud. The target's spirit rises as a specter in the space of its corpse or in the nearest unoccupied space. The specter is under your control, and takes it's turn immediately after yours. You can only have a number of specters equal to your WIS modifier under your control at one time. You may only use this technique while your Fiendish Form is active, and any specters under your control cease to exist when you revert to normal.