In the search for Oneness, some monks stumble across the secrets of one of the Mystical Affinities.  The Mystical Affinities are, Fire, cold, acid, lightning, thunder, poison, radiant, necrotic and force.  But the Way of the Mystical Affinity is a difficult path to walk and you cannot specialize in more than one path.

Mystical Affinity

Starting At 3rd level, you choose an Mystical Affinity from the following list: fire, cold, lightning, thunder, acid, poison, radiant, necrotic, or force.  Once chosen, this Affinity is locked in and cannot be changed at future levels.  Your Mystical Affinity determines your abilities in this subclass.

Mystical Flame

Starting At 3rd level you gain the ability to summon a Mystical Flame of your Mystical Affinity type.  This is treated as the produce flame cantrip with the following changes.  The flame that you produce is a special color dependent on your Mystical Affinity.  The damage done by the Mystical Flame is the same as your Mystical Affinity type.  Your spellcasting ability is based on your Wisdom.

Mystical Fists

Starting At 3rd level, you can spend 2 ki as a bonus action to wreath your fists in Mystical Fire for 1 minute.  Your unarmed attacks deal additional damage equal to your martial arts die in a damage type the same as your mystical affinity.  This does NOT effect monk weapons, only the monk’s unarmed attacks.  At 11th level, this damage increases to two times your martial arts die in damage.

Breath of Mystical Flame

Starting at 6th level, spend 1 ki as an action to breathe a flame of your Mystical Affinity type.  This ability works like the Dragon’s Breath (including multiple casts if concentration is held) but in your mystical affinity damage type.  This is treated as a spell level equal to your 1/2 your character level rounded up (ie. A 3rd level monk would cast this as a second level spell).  This spell uses your wisdom as a spellcasting modifier.

Mystical Immunities

Starting At 6th level, you gain resistance to your mystical affinity type.  At 11th level this increases to immunity to your mystical affinity type.  At 17th level, you heal hit points when hit by damage of a type that matches your mystical affinity.

Mystical Aura

Mystical Body

Starting at 17th level, you can spend 5 ki as an action to infuse all of your body with your mystical affinity energy, when you do this colored flames of your Mystical Affinity type, spreads across your body.  Your Mystical Fists are activated without a ki cost, your Mystical Breath is activated without a ki cost (and does not require concentration).  You can turn on and off your Mystical Aura as a free action.  In addition to these effects you heal hit points equal to twice your proficiency bonus at the start of each of your turns.  You also gain a bonus equal to your proficiency bonus to your armor class and saving throws.  This Mystical Body form lasts for 1 minute.