Improved Way of the Four Elements

Monks that follow the Way of the Four Elements give themselves to the four primal elements of the material plain - earth, wind, water, fire. They use these elements to empower their attacks and guide their path as they strike out into the lands they find themselves. 

Elemental Mastery

Upon taking this subclass at 3ed level, you monk begins to attune to the elements. Choose one of the four elements to attune to. An additional element will be attuned at level 11. You get all of the following abilities of your attuned element(s), plus one other element of your choice.

Air

Your monk becomes attuned to air. Additionally, you learn the cantrip Gust

Earth

Your Monk becomes attuned to Earth. Additionally, you learn the cantrip Mold Earth.

Fire

Your monk becomes attuned to fire

Water

Your monk becomes attuned with the ceaseless tides and flowing nature of water. 

Elemental Fists

Starting at 3ed level, you can superimposes an elemental body part onto one of your own in order to deal increased damage of a certain type equal to your current martial arts die plus your wisdom modifier. You can only superimposes elements that you are currently attuned to. You can only use 1 elemental superimposition per attack roll. For each additional Elemental Fist you use on your turn, the cost increases by 1 ki point. For example, if you both action and bonus action attack, and elemental fist on both, you would expend 1 ki point for the first and 2 ki points for the second.  You can decide when to use this feature at any time, like a Paladin's smite.

Elemental Fists - Air

You superimpose a fist of hardened air over your fist, dealing an additional martial arts die plus your wisdom modifier force damage.

Elemental Fists - Earth

You superimpose a rocky fist around your own, dealing an additional martial arts die plus your wisdom modifier bludgeoning damage. 

Elemental Fists - Fire

You superimpose a fiery fist over your own, dealing an extra martial arts die plus your wisdom modifier fire damage.  

Elemental Fists - Water

You superimpose a watery fist over your own, dealing an additional martial arts die plus your wisdom modifier cold damage.

Elemental Defenses

At 6th level, you learn how to use the elements to defend yourself in combat. 

Air

As a reaction to being attacked with a melee attack, you can spend 2 ki points to become air, reducing damage taken by half your monk level and allowing you to move up to 10ft without incurring any attacks of opportunity.

Earth

As a reaction to someone attacking you, you can spend 2 ki point to cover yourself in elemental earth, reduce any damage taken by an amount equal to half your monk level, and gain advantage on CON and STR saving throws until the start of your next turn.

Fire

As a reaction to someone attacking you with a melee attack, you can spend 2 ki point to cover your body in elemental fire, reducing the damage you take by an amount equal to your monk level and dealing 2d6 fire damage to any melee attacker. This increases to 3d6 at 11th level and 4d6 at 17th level. 

Water

As a reaction to someone attacking you with a melee attack, you can spend 2 ki point to become elemental water. This allows you to reduce the damage taken by an amount equal to half your monk level rounded up, and allows you as part of that reaction to attempt to grapple any creature that attacks you with a melee attack. You will have advantage on your roll to grapple, the enemy will have disadvantage. 

Elemental Aptitude

Your mastery of the elements allows you to use various elements to enhance your mobility in combat. Additionally, basically your cantrips get more powerful. I'm far to lazy to actually DNDbeyond this at the current time, maybe I'll do it later. You get do do coolermonkstuff.

Air

As a bonus action, you can spend 3 Ki points to become one with air, giving you a flying speed equal to twice your walking speed for 1 minute. While in this form, you do not trigger opportunity attacks. You must reform to take any other action, though reforming costs no action.

Earth

As a bonus action, you can spend 3 KI points leap into the air and then become one with the earth, slamming back to the earth as a boulder or other such heavy object. This has up to 15ft of lateral movement, and requires 30ft of free space above it to use. Upon landing, release a small shockwave, forcing all creatures within a 15ft sphere, centered around the point of impact, must make a Dexterity save against your Ki save DC. On a failure, they take 6d8 bludgeoning damage and are knocked prone. A successful save results in half damage and no prone. The initial leap does not incur attacks of opportunity.

Fire

As a bonus action, you can spend 3 Ki points to become a bolt of fire, shooting out in a straight line 5ft wide and as long as your current walking speed. Each enemy you hit must make a DEX save, on failure taking 6d6 fire damage, halved on success. This fire can light objects that aren't being worn or carried, but that is up to the player to decide.

Water

As a bonus action, you can spend 3 ki points to become a pool of water 20ft in diameter. Your movement speed is halved, and the only action you can take is to restrain any creature of your choice. To resist the restraint, creatures must succeed on a DEX save or be restrained. Additionally, they take 4d8 cold damage, halved on success. This effect lasts until the start of your next turn.

Elemental Projector

At 17th level, you learn how to project your elements in a wide range around you. 

Air

For the cost of 10 ki points, you can summon a tornado with a 40-foot radius sphere within 200 feet of you. All creatures must succeed on as STR save against your Ki save DC or be pulled into the center of the sphere. All creatures take 2d10 Force damage, halved on success. If a creature hits another creature as a result of getting pulled into the center, they both take 8d8 Bludgeoning damage.

Earth

For the cost of 10 Ki points, you can stomp the ground in order to create an earthquake in a 60ft cone in front of you. All creatures must make a DEX save against your Ki save DC or fall prone. Additionally, creatures will take 8d12 bludgeoning damage, halved on success. 

Fire

For the cost of 10 ki points, you can designate a 30-foot diameter sphere within 120ft of you. You then summon  a large mass of fire to spring from your hands, similar to a fireball spell. This deals 8d10 fire damage, halved on a successful DEX save against your KI save. 

Water

For the cost of 10 Ki points, you become a tidal wave and move 60ft in a straight line in any direction. Everything in your path must succeed on a CON save against your Ki save DC or take 8d8 cold damage and be dragged with you to your end point (obeying the rules that no two creatures can share the same space, effectively creating a huge pile-up) Success on the save means that the creature takes half damage and is not dragged.