Elementalist Monks have a deep connection with the Elements. They learn to shape, control, and incorporate the elements into their daily lives and even fights. Most Monks that follow this path choose to specialize in connecting to one single element; Air, Water, Earth, or Fire. And through their connections with the element that they chose, they become more in tuned with it allowing them to influence more.

Elemental Fighting

Fire: When you take the attack option, you can choose to shoot fire from your unarmed attacks increasing their range to 30 feet, and dealing fire damage equal to your Martial Arts Die. You also learn how to cast Produce Flame, as well as Control Flames, increasing the 5 ft cube to a 15 ft cube. 

Earth: When you take the attack option, and Earth (whether worked or unworked) is available, you can choose to form pillars, shoot rocks, or something along the lines of that instead, increasing their range to 30 feet and dealing Bludgeoning damage equal to your Martial Arts Die. You also learn the Mold Earth cantrip, ignoring the loose earth restriction and increasing the 5ft cube to a 15 ft cube. 

Water: When you take the attack action and have access to water you can instead use the water to attack, whether using water to deal Bludeoning Damage equal to your Martial Arts Die or ice dealing Piercing equal to your Martial Arts Die. You also learn the Shape Water cantrip increasing the 5ft cube to a 15ft cube and you can use it to Restrain a target with ice, the target can make a Strength or Dexterity Saving Throw against your Ki Save DC.

Air: When you take the attack action and air is present, you can choose to air to attack dealing Force damage equal to your Martial Arts Die and can expend 2 of your attacks to force a target to make a Strength Saving Throw against your Ki Save DC or be knocked prone. You also learn the Gust cantrip and can move most creatures and objects. 

Advanced Techniques

Fire: You release a gout of flame in a 15ft cone or a 30ft x 5ft line dealing damage equal to twice your Martial Arts Die. On a failed save, the target takes full damage and is set aflame, taking 1d6 fire damage on the start of their turn until the fire is put out. On a successful save, the target takes half damage and is not set aflame. Each additonal Ki Point spent above 2 allows you to add 5ft to the cone or the line (either length or width).

Earth: You perform an attack using earth that is so forceful that it launches the target dealing damage equal to twice your Martial Arts Die and launches them 30ft. On a failed save. the target takes full damage and is launched 30ft as well as knocked prone. On a successful save, the targer take half damage, is launched only the distance, and is not knocked prone. For each additional Ki Point spent above 2 allows you to target an additional target. 

Water: With the appropriate amount of water available, you can create a wave of water 15ft high, 5ft long, and 30ft wide and can push it forward a total of 30ft; dealing damage equal to twice your Martial Arts Die and is carried until the wave dissipates. On a failed save, the targets take full damage and is carried until the wave dissipates. On a successful save, the targets take half damage and isn't carried. For each Ki Point spent above 2 you can force one person to roll at disadvantage/Ki Point. 

Air: You can make the air in a 15ft sphere swirl around you violently dealing damage equal to twice your Martial Arts Die, pushing anyone in the sphere outside of the sphere, and preventing ranged attacks and anyone from entering it. On a failed save, tanyone in the sphere takes full damage and is pushed out of the sphere. On a successful save the taget takes no damage but is still pushed out of the sphere. For each Ki Point spent above 2, allows you to choose one target/Ki Point that can leave and enter the sphere without taking damage.

Shape the Elements

Fire: When you cast Control Flames the cube increases to a 30ft cube, and you can now coat weapons that you are holding in fire allowing them to deal extra fire damage equal to your Martial Arts Die. You can also choose to expend 3 Ki Points to create a Wall of Fire 10ft tall and 30ft long, that deals damage equal to your Martial Arts Die, this can be used as a reaction. 

Earth: When you cast Mold Earth the cube increases to a 30ft cube, and you can now cast Move Earth at will. You can also choose to expend 3 Ki Points to create a Wall of Earth 15ft tall and 30ft long, this can be used as a reaction. You can also spend 1 Ki Point to encase your body in Earth adding +2 to your overall AC.

Water: When you cast Shape Water the cube increases to a 30ft cube, and you can now cast Control Water at will. You can also choose to expend 3 Ki Points to create a Wall of Ice 30ft tall and 30ft long, this can be used as a reaction. You can also expend at least 1 Ki Point to heal a target, the target takes healing equal to your Martial Arts Die per Ki Point Spent, as long as water is available.

Air: Your Slow Fall now prevents all damage taken, difficult terrain does not hinder you anymore, and your base walking spend increases by 10ft. You can spend 3 Ki Points to cast Levitate on yourself.

Elemental Attunement

Fire: You can choose to expend 5 Ki Points to cast Lightning Bolt at 6th level using your Martial Arts Die for damage, you are also able to use Deflect Missiles on Lightning Damage. 

Earth: You gain a Burrowing Speed equal to your Walking Speed and gain Tremorsense out to 60ft. You are able to use Deflect Missiles on any ranged attack; however you cannot throw them back if you do this. When you cast Mold Earth or Move Earth you can expend 1 Ki Point per 5ft of Lava available and you can influence lava as well as the earth available.

Water: You gain a Swimming Speed equal to your Walking Speed and can extract water from your environment (as long as the environment allows for it) by expending 1 Ki Point per gallon of water extracted. By doing this the object you extracted water from wilts. You can also use Deflect Missiles on ranged Bludgeoning, Fire, Cold, Piercing, and Slashing damage as long as water is available; however you cannot throw them back if you do this.

Air: You gain a Flying Speed equal to your Walking Speed and can grant a Flying Speed equal to half your Walking Speed to 1 target/Ki Point spent. You can also use Deflect Missiles on all projectiles; however, you cannot throw them back if you do this. You can also choose to expend 3 Ki Points and create a cylinder of air 10ft in diameter and 60ft high, anyone already in or entering the cylinder takes damage equal to 11d(Martial Arts Die). On a failed save, the target(s) take full damage and is lifted up 60ft. On a successful save the target takes half damage and isn't lifted but the ground acts like difficult terrain. 

Perfect Embodiment

Fire: You are now immune to fire damage and the effects of extreme heat and extreme cold. You can also expend 10 Ki Points to radiate intense heat in a 30ft sphere centered on you, replicating the effects of extreme heat and dealing fire damage equal to your Martial Arts die to everyone in the sphere for 10 minutes. All abilities granted by this subclass other then the level 17 ability cost half ki. When you cast Control Flames the cube increases to 120ft.

Earth: You now have tremorsense out to 120ft and the range of your Mold Earth and Move Earth now increases to 120ft as well. You can expend 10 Ki Points to become one with Earth, when you do this you can make opportunity attacks on anyone in range of your attacks without using up your reaction. All abilities granted by this subclass other then the level 17 ability cost half ki.

Water: You are now immune to Cold Damage and when you cast Shape Water or Control Water the range increases to 120ft. You can choose to expend 10 Ki Points to create a gargantuan monster centered on you; your size is gargantuan and have a temporary HP equal to 10 times your Monk Level. It lasts for 10 minutes or until your temporary HP is gone, you can dismiss this ability as a bonus action. All abilities granted by this subclass other then the level 17 ability cost half ki.

Air: You now longer have the need to breathe and can expend 10 Ki Points to create a vacuum that sucks the air out of a 30ft sphere suffocating everyone in the sphere, this effect lasts for 10 minutes or until you dismiss it as a bonus action. When you fly you are no longer affected by exteme wind or anything that would otherwise prevent you from flying or staying aflight. All abilities granted by this subclass other then the level 17 ability cost half ki.