You follow a monastic tradition that teaches you how to channel and manipulate the elements through your ki. You learn to do so through a variety of fighting stances, each meant to facilitate a fundamental connection to its respective element and to allow you to empower your blows with that element. 

Though all members of this tradition learn to harness all the elements, all eventually develop a particular affinity for one over the others. This affinity allows them to achieve mastery over that element not possible to those without it. 

Primordial Stance

At 3rd level, when you gain this monastic tradition, you learn the four elemental stances. Stout Mountain is for elemental earth, Mystic River is for elemental water, Coursing Wind is for elemental air, and Searing Heat is for elemental fire. 

As a bonus action, you may assume a Primordial Stance. You cannot be in more than one stance at a time. When you assume an elemental stance, or as a bonus action while you are in one, you may spend Ki points to fuel your stance’s advanced techniques. Stances last until you end them as a bonus action, change stances as a bonus action, you are incapacitated, or die.

Stout Mountain

When you assume this defensive form, you become as resilient as a mountain and gain a +1 bonus to your AC, so long as you are using Unarmored Defense. 
Advanced Technique: Implacable Cliff 
By spending 1 Ki point, you channel the stubbornness of  a mighty cliff face. For one minute, you may not be moved against your will or knocked prone so long as your feet are touching the ground or an earth or stone surface. 

Mystic River

When you assume this balanced form, you begin to move like water; sometimes slow and gracefully, other times with unparalleled fury. While in the Mystic River stance, your mind becomes like water, and you have advantage on saving throws against being charmed or frightened. Additionally, whenever you hit with your unarmed attacks, you may choose to deal cold damage instead. When you choose to deal cold damage, you gain a +1 bonus to hit.
Advanced Technique: Flowing Water Crushes Rock
By spending one Ki point, you can imbue yourself with the force of a raging river. The next creature or object you hit with an unarmed attack takes an additional 2d6 bludgeoning damage and must make a Strength saving throw or be pushed back 10 ft. Once you hit with this advanced technique, it immediately ends. 

Coursing Wind

When you assume this agile form, you begin to move like the wind. Your movement speed increases by 5 ft. so long as you are in this stance and you have resistance to fall damage. Additionally, when you hit with your unarmed attacks, you may choose to do thunder damage instead. 
Advanced Technique: Run Like the Wind
By spending 2 Ki points, you may double your movement speed for your turn and immediately take the Dash action as a part of the bonus action used for this advanced technique. If you move at least 10 feet as a part of this Dash action before making an attack, you deal an additional martial arts die of damage on the first attack.

Searing Heat

When you assume this offensive form, you strike with the fury of an inferno. You may choose to have your unarmed attacks deal fire damage, and if they do, the range of your unarmed attacks extends to 10 ft and you gain a +1 bonus to damage with them. 
Advanced Technique: Gout of Flame
By spending one Ki point, you can replace one of your attacks with a gout of flame. You send out jet of flame in a 15 ft. cone and all creatures in that area must make a Dexterity saving throw, taking 2d6 + your marital arts die fire damage, or half as much on a successful save. If you have the Extra Attack feature, you may replace more than one attack, with each additional one costing one more Ki point than the last. 

Primordial Stance Mastery

You have gained enough experience with the four primordial stances to develop an even more advanced variant of one of them. 

When you reach 6th level, choose one of the following enhancements for your Primordial Stances. 

Stout Mountain

Mastery Technique: Eternal Mountain
When you assume the Stout Mountain form, or as a bonus action while you are in it, you can spend 3 Ki points to imbue yourself with the endurance of a mighty mountain. For one minute, or until you are incapacitated or die, you gain advantage on Strength saving throws and resistance to all nonmagical bludgeoning, slashing, and piercing damage. Additionally, you create a 5-foot aura of swirling rocks and earth that grants all friendly creatures besides yourself half-cover.

At 11th level, the density of the swirling earth increases to the point that you benefit from the half-cover as well.

Mystic Water

Mastery Technique: Still Waters
When you assume the Mystic Water form, or as a bonus action while you are in it, you may spend 1 Ki point to channel pure, soothing elemental water to revitalize yourself or a creature you touch, granting them temporary hit points equal to 1d10 + your Wisdom modifier. Whenever a creature that has these temporary hit points recovers hit points, they gain a bonus to that healing equal to your Wisdom score modifier.

At 11th and 17th levels, this ability grants an additional d10 of temporary hit points, up to a maximum of 3d10 + your Wisdom modifier.

Coursing Air

Mastery Technique: Thunderbolt and Lightning
When you assume the Coursing Air form, or as a bonus action while you are in it, you may spend 4 Ki points to imbue yourself with lightning. For one minute, whenever you make an unarmed attack or an attack with a monk weapon, you deal lightning damage. Additionally, as an action, you can choose to shoot a bolt of lighting out in place of your normal attack. All creatures and objects in a 30 ft. line must make a Dexterity saving throw, taking four of your martial arts dice in lightning damage, or half as much on a successful save. Each time your martial arts die increases, you deal an additional die of damage onto the bolt of lightning. For example, if your martial arts die is a d6, a creature that failed its saving throw would take 4d6 lightning damage, and if your martial arts die was a d8, you would roll 5d8 points of lightning damage.

Searing Heat

Mastery Technique: Atavistic Inferno
When you assume the Searing Heat form, or as a bonus action while you are in it, you may spend 3 Ki points to wreathe yourself in flames for 1 minute. You shed bright light in a radius of 20 ft., and dim light for a further 20 ft. beyond that. You gain resistance to fire damage. Additionally, all your unarmed and monk weapon attacks deal fire damage and gain a bonus to damage equal to your Wisdom modifier.

Primordial Paragon

At 11th level, you have deepened your connection to the four prime elements to the point where you are able to empower your unarmed attacks. Whenever you are in a Primordial Stance, you gain a +1 bonus to hit and to damage with your unarmed strikes.

Higher Elemental Stances

At 11th level you have mastered the base elements and are ready to begin channeling the higher elements of radiant energy, necrotic energy, and arcane force. You learn three new stances; Luminescent Bloom for radiant energy, Void Touch for necrotic energy, and Sublime Strikes for force.

Luminescent Bloom

With this stance you channel the life empowering energy of the Positive Energy Plane. When you enter into this stance, you begin to shed bright light for a 10 ft. radius, and dim light for 10 ft. beyond that. Your unarmed attacks deal radiant damage in this stance, and if you hit an undead it takes an extra martial arts die of damage. Additionally, you gain a +2 bonus to hit with your unarmed strikes.

Advanced Technique: Solar Flare 
When you hit a target with an attack, you may spend 1 Ki point to deal an extra 4d6 radiant damage to the target.

Void Touch

In this stance you empower your strikes with necrotic energy from the Negative Energy Plane. Your unarmed attack deal necrotic damage while in this stance. When you strike an enemy with an unarmed attack, you may choose to gain temporary hit points equal to the damage dealt plus your Wisdom modifier. You may do this a number of times equal to your Wisdom modifier, after which you need to take a long rest before you can do so again. Additionally, you gain a +2 bonus to the damage of your unarmed attacks.
Advanced Technique: Call of the Void
As a bonus action, you can sacrifice some of your own energy to the Negative Energy Plane to continue to channel its power. By spending 3 Ki points, you may gain temporary hit points from this stance again, as if you had finished a long rest.

Arcanic Gyre

You tap into the Weave itself to empower your blows in this stance. Your unarmed attacks deal force damage and you gain a +1 bonus to attack and damage rolls with them. Additionally, you may spend 3 Ki points to cast dispel magic with a range of touch, using Wisdom as your spellcasting modifier.
Advanced Technique: Deflect Spell
When you are subjected to a spell that targets only you, you may use your reaction to attempt to deflect it back at the caster. You must spend a number of Ki points equal to the level of the spell to do so, if you do not have the Ki points required, your reaction is wasted and the spell functions as normal. If you have the required Ki points, you can make a Wisdom check with a DC equal to 10 + the spell's level. If you succeed, the caster is subject to the effects of the spell as if you had cast is using Wisdom as your spellcasting modifier. If you fail the check, the spell functions as normal.

Transcendant Mastery

At 17th level you become a living conduit for the elements, achieving mastery over radiant, necrotic, or force damage. You learn a new mastery technique for Luminescent Bloom, Void Touch, or Arcanic Gyre.

Luminescent Bloom

Mastery Technique: Solar Equinox
As an action, you use an action to unleash a blast of radiant energy in a line 5 ft. wide and 60 ft. long.  All creatures in that line must make a Dexterity saving throw, taking 4d6 radiant damage, plus an additional 4d6 for each Ki point spent, up to a maximum of 3 Ki points, or half as much damage on a successful saving throw.

Void Touch

Mastery Technique: The Goal of All Life is Death
As an action, you make an unarmed attack against one creature dealing an additional 10d6 necrotic damage and expending 4 Ki points on a successful hit. If the target is reduced to 0 hit points by this attack, it's soul, spirit, or essence is sucked into the Negative Energy Plane and lost forever, unless a wish spell is used to retrieve it.

Arcanic Gyre

Mastery Technique: Weave Warping
As a reaction, you may spend 1 Ki point to cast the shield and absorb elements spells on yourself and on an ally within 30 ft. of you simultaneously (the reaction used for the spells is the same as the one used to trigger this ability).

Alternatively, when a creature within 30 ft. of you is forced to make a saving throw from a spell or magical effect, you can use your reaction to expend 1 Ki point to grant them advantage on the saving throw, 3 Ki points to impose disadvantage on the saving throw, or 5 Ki points to allow the creature to treat their saving throw as if they had rolled a 20 on the d20.