The Way of the Mutilated uses their body in ways no sane person would. One way or another, this being was blessed with regeneration and now destroys their own body to maximize damage. The tearing of skin, the snapping of bones, and the sloshing of their own guts are common sounds to a Mutilated monk.

Limb From Limb

When you choose this subclass at level 3, you gain the ability to tear apart your own body and fashion weapons from the viscera. As a bonus action, you may create one bodily weapon from the list. Your are proficient and these count as monk weapons for you. As an additional bonus action, you may dismiss the weapon by ingesting it back into your own body.

Femur Javelin- 1d6 piercing, Thrown 30/120

Arm- 1d8 bludgeoning, You have only one arm while using this weapon

Spinal Flail- 1d8 bludgeoning, Reach and Versatile, You take 1d10 necrotic damage when summoning this weapon as you pull your head and entire spine from your body

In addition, you may reattach any lost limbs or body parts with this feature.

At 6th level, the damage from these weapons counts as magical for the purpose of overcoming resistance and immunity to nonmagical attacks and damage.

Masochist

Starting at 3rd level, your body repairs itself through the ecstasy of mutilation. When you end your turn in combat after taking or dealing damage, you regain hit points equal to your Martial Arts die.

This feature upgrades and becomes two Martial Arts dice at level 11 and three Martial Arts dice at level 17.

Shin Splints

Starting at 6th level, your attacks devastate both your own body and the opponents. When making an unarmed attack, it deals an additional 2d4 piercing damage to the creature as your fractured bones pierce the skin.

Fragility

At 11th level, you imbue your barrage of attacks with your curse of regeneration to devastate both you and the enemy. When targeting a creature with your Flurry of Blows, you may give them vulnerability to piercing damage and add an additional Martial Arts die to each blow. You take damage equal to half of the damage dealt. The damage taken by this feature cannot be reduced in any way for both you and the targeted creature.

You may use this feature a number of times equal to your Dexterity modifier (minimum of 1). You regain all uses after a Long Rest.

Weaponized Gore

At 17th level, the destruction of your own body leads to the destruction of other's. Whenever a creature hits you with a melee attack, they take 10d4 piercing damage as your bones stab through your flesh to retaliate. This damage cannot be reduced in any way.

In addition, as a reaction you may spend 3 Ki points to regain hit points equal to the damage dealt by this feature.