Earth, Fire, Air, Water
The Way of the Four Elements Reborn teaches initiates how to extend their ki into the world around them. Through rigorous training and keen awareness, practitioners of this monastic tradition harness the power of the elements to devastating effect.
(Note: I did not, nor do I claim to have, made this subclass. For the original source please search Way of the Four Elements Reborn on Nerdachy.com)

Separation is an Illusion

Everything is connected; all life, all magic, all four elements. The Way of the Four Elements teaches initiates that all is one and one is all. Separation–even that of the elements–is an illusion, as each merely extends into the others. The intuitive find that shifting stances among the elements is as effortless as breathing.

Balance in All Things

Life is about balance. The four elements exist in a cycle of push and pull, ebb and flow, yin, and yang. By weaving the elements in balance, initiates of this monastic tradition understand the necessity of balance in all areas of life. Without balance, there is no peace, and any idea taken to the extreme results in imbalance, which inevitably leads to void. As an initiate of the Way of the Four Elements, you master the concept of balance and achieve inner and outer peace in equal measure

Spellcasting

Some features of The Way of the Four Elements Rebornallow you to cast spells. When you cast a spell using a feature from this class, you ignore any material or verbal component requirements for spells, and if a spell from these features has only material or verbal components, you substitute those components for somatic components.

Wisdom is your spellcasting ability for all spells and abilities granted by this subclass. Your spell save DC equals 8 + your proficiency bonus + your Wisdom modifier, and your spell attack bonus equals your proficiency bonus + your Wisdom modifier.

The ki point cost for casting spells through this subclass equals 1 + the level of the spell. 

Beginning at 5th level in this class, you can spend additional ki points to increase the spellcasting level of your spells that can be upcast. For each additional level you upcast a spell, you must spend 1 additional ki point. The maximum level at which you can cast a spell through this class equals your monk level, divided by 3 (rounded down).

Elemental Attunement

Beginning when you choose this path at 3rd level, you gain the ability to manipulate the elements around you. As a bonus action on your turn, you can create one of the following effects:

• You create a harmless sensory effect using the elements around you, such as a puff of air, a shower of sparks, a spray of mist or a rumbling of stone.
• You instantaneously light or snuff a candle, torch or other small fire (such as a campfire).
• Chill or warm up to one pound of nonliving material for up to one hour.
• Cause earth, fire, air, or water within a 1-foot cube to move and/or shape itself into a crude form you designate for up to one minute.

You can have up to five such effects active at a single time, as long as you maintain your concentration as though you were concentrating on a spell.

Casting Elemental Spells

Some elemental disciplines allow you to cast spells. See the Spellcasting section for the general rules of spellcasting. To cast one of these spells, you use its casting time and other rules, but you don’t need to provide material components for it.

Elemental Stance

Also at 3rd level, you learn to harness one of the 4 main elements, chose a stance of your choice, you can then enter that stance by using a bonus action. Each Elemental Stance grants you specific benefits as listed under each element’s Elemental Stance below. Each Elemental Stance lasts until you dismiss it (using an action), until you are incapacitated, or until you switch to a new Elemental Stance as a bonus action on your turn.

You can learn one additional Elemental Stance that you do not know and unlock new features of each Elemental Stance when you reach 6th, 11th and 17th level in this class.

Stance of Earth

Beginning at 3rd level, you gain the following benefits while you are in Stance of Earth:

• Earth’s Embrace. You can cast the mold earth cantrip.
• Rooted Defense. When you move 15 feet or less on your turn, your Armor Class increases by 2. This bonus remains until you move for more than 15 feet in one turn.
• Stone Anchor. While you are standing on nonmagical earth or stone and have moved 15 feet or less on your turn, you cannot be forcibly pushed or pulled until the beginning of your next turn.

At 6th level, you gain the following additional benefits while you are in Stance of Earth:

• Carve the Path. You gain a burrowing speed of 20 feet.
• Stone’s Throw. You can attack by throwing rocks. When you do, you make a ranged weapon attack with a short range of 60 feet and a long range of 90 feet. These rocks are monk weapons for you, and count as magical for the purpose of overcoming resistance and immunity to nonmagical damage.

At 11th level, you gain the following additional benefits while you are in Stance of Earth:

• Grasping Tomb. As an action, you spend 3 ki points to choose 1 creature within 60 feet of you. The creature must make a Dexterity saving throw. On a failure, the creature is grappled and restrained, as the earth itself rises to grasp it. A creature that is restrained in this way can use its action to attempt to break free of this effect. The DC for breaking free is your ki save DC. Creatures that are more than 10 feet above the ground automatically succeed on the initial saving throw against this ability.
• Knock, and It Shall Open. You can spend 5 ki points to cast stone shape.

At 17th level, you gain the following benefits while you are in Stance of Earth:

• Sculpter’s Touch. You can spend 6 ki points to cast transmute rock.
• Mason’s Hedge. You can spend 6 ki points to cast wall of stone.

Stance of Fire

Beginning at 3rd level, you gain the following benefits while you are in Stance of Fire:

• Fire’s Embrace. You can cast the control flames cantrip.
• Energy Burn. Your unarmed strikes’ reach increases by 15 feet, and you can cause their damage type to be fire. If your unarmed strike extends into your expanded reach, the damage must be fire.

At 6th level, you gain the following additional benefits while you are in Stance of Fire:

• Scathing Will. You add your Wisdom modifier to all fire damage you deal.
• Inner Flame. You can cast produce flame, and you can cast it as a bonus action on your turn.
• Dragon’s Breath. You can spend 2 ki points to cast burning hands

At 11th level, you gain the following additional benefit while you are in Stance of Fire:

• Phoenix Screech. You can spend 4 ki points to cast fireball.

At 17th level, you gain the following benefit while you are in Stance of Fire:

• Hedge of Passion. You can spend 5 ki points to cast wall of fire.

Stance of Air

Beginning at 3rd level, you gain the following benefits while you are in Stance of Air:

• Air’s Embrace. You can cast the gust cantrip.
• Flying Leap. When you make an attack, you can spend 1 ki point to fly up to 15 feet. This movement does not provoke opportunity attacks.

At 6th level, you gain the following additional benefits while you are in Stance of Air:

• Windy Strike. You can cast the shillelagh cantrip, as the wind itself fuels your strikes.
• Leaf on the Wind. You do not take damage as a result of falling while you are not incapacitated.
• Whistling Gale. You can spend 2 ki points to cast gust of wind.

At 11th level, you gain the following additional benefit while you are in Stance of Air:

• Sentinel’s Breath. You can spend 3 ki points to cast warding wind.

At 17th level, you gain the following benefit while you are in Stance of Air:

• Guide the Four Zephyrs. You can spend 6 ki points to cast control winds.

Stance of Water

Beginning at 3rd level, you gain the following benefits while you are in Stance of Water:

• Water’s Embrace. You can cast the shape water cantrip.
• Surge Assault. Your unarmed strikes’ reach increases by 15 feet, and you can cause their damage type to be bludgeoning or cold.

At 6th level, you gain the following additional benefits while you are in Stance of Water:

• Tendril Form. You can cast the thorn whip cantrip. It manifests as a tendril of water instead of a thorny vine. You can cast this cantrip as a bonus action on your turn.
• Biting Cold. You can cast the primal savagery cantrip, as claws of frozen, acrid water form on your fingertips. You can cast this cantrip as a bonus action on your turn.
• Ebb and Flow. As an action, you can spend 1 ki point to choose an area of water within 210 feet of you that is no larger than 30 feet on a side. You can change water to ice in the area, and vice versa. You can reshape ice in the area in any way you wish. You can raise or lower the elevation of water, ice or steam, and you can cause steam, fog or mist in the area to appear or disperse entirely. You can also dig a trench with the ice or water, but you cannot use the ice or water to cause damage a creature.

At 11th level, you gain the following additional benefits while you are in Stance of Water:

• One with the Water. You gain a swimming speed equal to your current speed, and you can breathe underwater.
• Healing Flow. As an action, you can touch a creature’s flowing life energy and spend a number of ki points up to your monk level, divided by four (rounded down), to augment the creature’s natural recovery. For each ki point you spend, a creature spends one hit die and adds its Constitution modifier and your Wisdom modifier to the amount of hit points recovered.
• Resurgent Ki. You can spend 3 ki points to cast lesser restoration.

At 17th level, you gain the following benefits while you are in Stance of Water:

• Liquid Command. You can spend 5 ki points to cast control water.
• Ever flowing Globe. You can spend 5 ki points to cast watery sphere.

Elemental Redirection

Beginning at 6th level, you can spend 2 ki points to cast absorb elements.

Elemental Mastery

Starting at 11th level, you can cast mold earth, control flames, gust, and shape water even when you are not in the associated Elemental Stance. You can cast any of these cantrips as a bonus action.

Elemental Avatar

Beginning at 17th level, you can cast each of the following spells once:

• Stance of Earth: investiture of stone
• Stance of Fire: investiture of flame
• Stance of Air: investiture of air
• Stance of Water: investiture of ice

Once you cast one of these spells using this ability, you become unable to enter the associated Elemental Stance listed alongside it. You regain the ability to reenter that Elemental Stance after you finish a short or long rest.

You regain use of all of these spells through this feature after you finish a long rest.