Base Class: Paladin
In a world teeming with evil and darkness, some crusaders find that revealing evil by the light of day is not enough to stop it — evil must be purged to ashes itself. A growing respect for the cleansing power of divine fire leads these warriors to the Oath of Purification. Known for leading torch-wielding mobs, organizing ruthless inquisitions, and putting evil to the pyre, these paladins are devoted to purity by flame.
Tenets of Purification
With their rigid adherence to the concept of purity, those who follow the Oath of Purification rarely deviate from swearing to the purest conceptions of the oath's tenets. The oath emphasizes purity, but its followers run the gamut of alignments based on what they personally believe to be pure and what they see as corruption. The tenets of purification are:
Banish the Darkness. With darkness comes terror, and with the light of fire comes courage. The purity of my purpose must drive out the uncertainty, fear, and doubt I encounter.
Cleanse All, Even Oneself. Evil and corruption must be cleansed at every turn, no matter the cost. If evil is given time to fester, it will spread like a cancer. If corruption takes hold within my heart, it too must be cleansed before anything else.
Leave No Trace of the Evil. If those who come after can glean the truth of my enemies' evil from the ashes I leave, it means the ashes were not burned enough. Justice, sagacity, honesty, and all other such concerns are secondary to cleansing evil so thoroughly that it is completely forgotten.
Purity Only Through Pain. There is no painless method for cleansing corruption, even within myself. Those who seek to purify without causing pain will fail to purify anything.
Share the Flame. As one torch can light another, my righteous flame of purity can inspire others who are not yet corrupted to take up my cause, and I will lead those with smaller flames until they grow like a blazing beacon against the night.
Channel Divinity
When you take this oath at 3rd level, you gain the following two Channel Divinity options.
Cloaked in Fire. You can use your Channel Divinity to wreathe yourself in magical golden flames. As an action, you become surrounded with fire that scorches your foes without harming you or your equipment. Each enemy creature within 10 feet of you must make a Dexterity saving throw. A target takes fire damage equal to 2d6 + half your paladin level on a failed save, or half as much on a success.
Until the start of your next turn, the flames continue to burn, shedding bright light in a 20-foot radius and dim light for an additional 20 feet, and each enemy creature that ends its turn within 10 feet of you takes fire damage equal to 2d6 + half your paladin level.
Purifying Flames. You can use your Channel Divinity to imbue a target with purifying flame that does not burn them. As an action, you fill one creature that you can see within 60 feet of you with divine fire, and any creatures that are inside the target's body or possessing the target take fire damage equal to twice your paladin level.
You can cure one disease on the target or end up to one effect causing it to be blinded, charmed, deafened, paralyzed, or poisoned. In addition, the target has advantage on Constitution saving throws until the end of your next turn, and the next time it hits with a weapon attack before the end of your next turn, the attack deals bonus fire damage equal to your paladin level + your Charisma modifier (minimum +1).
Oath Spells
You gain oath spells at the paladin levels listed.
Oath of Devotion Spells
Paladin Level | Spells |
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3rd |
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5th |
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9th |
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13th |
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17th |
Aura of Warmth
At 7th level, you gain an aura of warmth that tempers flame, banishes cold, and purifies toxins. While you are conscious, you and friendly creatures within 10 feet of you have resistance to cold damage, fire damage, and poison damage.
At 18th Level the range of this aura increases to 30 feet.
Purge by Fire
Starting at 15th level, when you deal fire damage with a spell or paladin class feature to a creature you can see within 120 feet of you, you can choose to instantly cast dispel magic on that creature, without expending a spell slot or requiring components. You can do this even if you do not have dispel magic prepared.
Once you have used this ability, you cannot use it again until you finish a short or long rest.
Eradicating Flame
When you reach 20th level, you can use your action to ignite one weapon you are holding with divine flame. The weapon is engulfed in roaring golden fire that doesn't harm the weapon or you. This fire sheds bright light in a 20-foot radius and dim light for an additional 20 feet, and lasts for 1 minute or until you stop holding the weapon. The fire cannot be extinguished by normal means.
Melee attacks you make using the flaming weapon have advantage. When you hit with such an attack, the attack deals an extra 1d10 fire damage and 1d10 radiant damage, and if the target is flammable or is a creature, it is lit ablaze. Until someone takes an action to douse the fire, it takes 1d10 fire damage at the start of each of its turns. If damage from the attack or the fire kills a target, the target is turned to ash.
Once you have used this ability, you cannot use it again until you finish a long rest.

Gotcha, and thanks for the reply. I pretty much spent the entirety of my day learning how to create subclasses to overcome my OCD of not having it automatically added lol.
Alas, D&D Beyond won't allow Homebrew classes that add domain spells / expanded spell list spells to be shared with the public if any of those spells aren't from the SRD. That means even the more basic PHB spells, like searing smite, can't be added automatically for public releases. Unfortunately manually adding it is the only solution that we know of right now.
Just a heads up, searing smite isn’t showing up as an automatic spell learned at lvl 3. It has to be manually added.