Way of the Adamantine Mountain

This subclass is intended to give a unique playstyle to the monk that none of the standard or expansion subclasses offer. It exchanges speed for defensive options and the ability to make more reactions and expand the utility of existing monk abilities by altering them through the interaction with the mainstay of the subclass, Patience of the Mountain which improves patient Defense and turns it into a stance maintained as a bonus action at the start of each of your turns thus if you wish to make full use of the subclass you forgo the monk's iconic Flurry of Blows and/or bonus action unarmed attack.

You'll have slightly higher AC, resistances, higher martial arts die, thorns damage and several reaction options while using the subclass stance in exchange for half of your movement speed. Additionally to add variety to builds taking the subclass will allow you to use alternate stats for your Unarmored defense (Strength in place of Dex and/or Con in place of Wisdom) for those wanting an unorthodox monk build or potential multiclass that you may not normally consider gaining a slight bump at the final subclass level to both of these stats. It still uses Wisdom for determining DCs of monk abilities.

Level 3: Patience of the Mountain

At 3rd level upon taking Way of the Adamantine Mountain you may use your Strength in place of Dexterity and/or Constitution in place of Wisdom for your Unarmored Defense and when rolling for Initiative you may choose to act last in the turn order and if you do you may enter your Patience of the Mountain stance (see below) at no Ki point cost (normally it costs 1 Ki point), you may choose to do this even if surprised.

Instead of of the normal benefit of spending 1 Ki Point as a bonus action to activate Patient Defense, you enter the Patience of the Mountain stance which reduces your speed by half but grants resistance to all damage and adds half your proficiency bonus (rounded up) to your AC. On the start of your turn you may choose to maintain patience of the Mountain at no Ki point cost as a bonus action. Whenever you would suffer damage while Patience of the Mountain is active you regain the use of your reaction if you have used it. 

Additionally while maintaining Patience of the Mountain your martial arts die increases to 1d8 and bypasses material-based damage resistances and you deal critical damage when striking unattended objects with unarmed strikes or monk weapons. At 5th level this increases to 1d10. At 11th level this increases to 2d6. At 17th level this increases to 2d8 and your attacks with unarmed strikes and monk weapons treat immunities as resistance (this does not stack with itself, thus you do not bypass this resistance).

Level 6: Adamantine Deflection

At 6th level as an additional 2 Ki point cost when entering your Patience of the Mountain stance you may cause your ki to surge empowering your strikes which allows you to treat your unarmed strike damage as force damage. You may choose to make ranged attacks with unarmed strikes dealing force damage, treating their range as 20ft/60ft. Additionally, while Patience of the Mountain is active you can perform the following abilities:

• You may use your reaction to make an unarmed strike at an opponent that makes a melee attack against you, resolving after their attack. You may use this ability once per opponent per round, or you may spend 1 Ki point to reset the use(s) of this ability ability.
• You may use your reaction to make a ranged attack with an appropriate weapon against an opponent that makes a ranged attack against you (or includes you in a non-attack spell effect) and is within range, resolving after the attack or effect (in the case of effects that would prevent this attack, this reaction resolves just before the effect but the effect still occurs). You may use this ability once per opponent per round, or you may spend 1 Ki point to reset the use(s) of this ability ability.
• You may spend 1 Ki point as a reaction to negate a critical hit scored against you truing it into a normal hit, if you do you may make an appropriate attack (melee or ranged as above) back at the attacker, this does not count as an activation of either of the above abilities. Once per long rest this attack may be treated as a critical hit if it hits. You may spend 1 additional Ki point when activating this ability to gain advantage on the attack and a further 1 ki point to add your Wisdom to the attack roll. This attack is made using your unarmed strike modifiers to hit and deals Force damage equal to your unarmed strike damage bypassing damage resistance and immunity.

Any of these abilities may also be activated in conjunction with Deflect Missiles if appropriate.

 

Level 11: Reverberating Mountain

At 11th level when an enemy hits you with an attack (melee or ranged) while you have Patience of the Mountain active they suffer Force damage equal to half your proficiency bonus and gain one stack of Reverberating Mountain. These stacks on opponents last until the end of combat or activation (see below) but can be cleared by doing nothing on their following turn (passing their turn). When an attack would miss you you may instead choose to allow it to hit you taking minimum damage from the attack and applying 2 stacks of Reverberating Mountain instead of one.

You may spend 1 Ki points as an action (or 3 ki points as a reaction) to cause any opponents that have stacks of Reverberating Mountain within 60ft of you to take an amount of damage equal to twice your martial arts die as Force damage damage (Constitution save for half) and half the amount to opponents within 10ft of those opponents (Dexterity save for half). Each stack of Reverberating Mountain increases the save DC by 1 and causes an additional 1d6 points of Force damage. Opponents that take direct damage from this effect and fail their save have disadvantage for rounds equal to the stacks of Reverberating Mountain they had when this ability was triggered, they may use two actions to remove this disadvantage early.

You may instead spend 1 Ki point to expend all stacks of Reverberating Mountain from opponents within 60ft and heal for an amount equal to your martial arts die plus the number of stacks expended.

Once per long rest you may instead expend any number of stacks of Reverberating Mountain from opponents to regain a number of Ki points equal to half your level (rounded up) if the number of stacks expended is at lest equal to your proficiency bonus.

Level 17: Adamantine Physique

At level 17 you have cultivated your body to be as strong and tough as Adamantine granting you partial effects of Patience of the Mountain even when not maintaining the stance and increasing your Strength and Constitution scores by 2 points each.

At all times you have resistance to bludgeoning, piercing, and slashing damage and gain half your proficiency bonus to AC.

While Patience of the Mountain is active you are immune to critical strikes and the relevant ability from Adamantine Deflection now can be used once per short rest instead of once per long rest. Additionally you now count as dodging when Patience of the Mountain is active and may choose to activate Step of the Wind as part of the same bonus action used to maintain Patience of the Mountain (but not on the initial activation).