Way of the Adamantine Fist

Monks who follow the Way of the Adamantine Fist focus on harmonizing their Ki with the elemental power of Earth to harden their bodies and even pass through unworked earth and stone. As such, these monks focus more on their unarmed techniques than those who follow other Ways.

Stone Fist Technique

At level 3, you gain the ability to infuse your body with Ki in order to strike with great force. As a bonus action, you may spend 1 Ki point to increase the damage of your unarmed strikes by your proficiency bonus.  

This effect lasts for 1 minute. 

Metallic Body

At 6th level, your mastery of Ki infusion has become such that you can now harden your body against attack. When you activate Stone Fist Technique, you may choose to spend 1 Ki point to raise your Armor Class by one.  This bonus to your AC increases to +2 at 11th level and to +3 at 17th level.

This effect lasts for 1 minute.

In addition, you may use your reaction to reduce the effects of a critical hit to yourself. When you are hit by a critical, you may spend 1 Ki point to change the result to a normal hit. You will still take damage as normal, but no additional effects from the critical will apply.

Earthly Passage

At 11th level, you learn to move through rock and stone. When you use Step of the Wind, you may move up to your walking speed through nonmagical, unworked earth and stone without disturbing the material you pass through.  You may also Disengage or Dash as stated under Step of the Wind.

While traveling through the earth, you can detect and pinpoint the origin of vibrations within a radius equal to one half of your walking distance (rounded down), provided that the you and the source of the vibrations are in contact with the same ground/earth/stone.

You must exit the ground/earth/stone by the end of your turn. If you do not, you will suffer 3d10 force damage and be ejected into the nearest unoccupied space on the surface of the material you entered.

Adamantine Strike

At 17th level, your mastery of Ki now allows you to project your Ki beyond your body. When you utilize your bonus action Martial Arts Strike and hit your target, you can choose to expend 1 Ki point to release a burst of Ki in the form of a 30 foot cone originating from the point of impact. The target and each creature caught within the cone must make a Dexterity saving throw. Each creature takes 2d10 force damage on a failed save and is knocked prone, or half as much damage on a successful one (and resists being knocked prone).

You can increase the cone's damage by spending additional Ki points. Each additional point you spend, to a maximum of 3, increases the damage by 2d10. In other words, you may spend up to 4 Ki for a total of 8d10 force damage from the cone.