Oath of Enkindling

Paladins of the oath of Enkindling channel the elemental plane of Fire.  Enkindlers' spells and abilities can burn plants, set places on fire, burn skin, turn things to ash and cause burns, and if their fire is strong enough, melt metals. Eventually their fiery souls grow so hot they can even transmute fire damage into Radiant damage. Their area of expertise is always fire magics, and all of an Enkindler's spells must be fire magic. 

Those who swear the Oath of Enkindling follow this code:

A uncontrolled flame destroys all it touches, thus I master the flame and in doing so master myself.

As fire can purify and refine, so the flames I wield too shall burn away the dross in myself and others.

As fire is a tool of destruction, I will wield it to destroy those who destroy good.

As my enemies misuse fire, so I shall turn it to the service of the righteous.

I shall always fear the flame for it potential, but I shall not shirk from my duty to use it in the service of what is right.

Channel Divinity

When you take this oath at 3rd level, you gain the following two Channel Divinity options.

Burning Weapon. As an action, you can imbue one weapon that you are holding with smoldering hot energy, using your Channel Divinity. For 1 minute, you add your Charisma modifier to damage rolls made with that weapon (with a minimum bonus of +1). The weapon also emits bright light in a 20-foot radius and dim light 20 feet beyond that. If the weapon is not already magical, it becomes magical for the duration.

You can end this effect on your turn as part of any other action. If you are no longer holding or carrying this weapon, or if you fall unconscious, this effect ends.

Burn the Unholy. As an action, you present your holy symbol and speak a prayer censuring fey, fiends, and undead using your Channel Divinity. Each fey,  fiend, or undead that can see or hear you within 30 feet of you must make a Dexterity saving throw. On a success the creatures take 1d4 fire damage for two turns.

On failure, it is ignited and takes 1d6 fire damage. It takes this damage for 1d4+ your CHA modifier (minimum 0) each round. The creature may make a new saving throw to end this effect early at the end of its turn, but the DC increases by 1 for each failed save including the first one. This damage bypasses fire resistance and does half damage to beings with fire immunity.

Oath Spells

You gain oath spells at the paladin levels listed. You also gain two cantrips from the following list: Create Bonfire, Control Flames, Green-flame Blade, Fire Bolt, Produce Flame.

Oath of Enkindling Spells

Bright Soul

Starting at 7th level, your very soul is a bright burning flame of purification. Whenever you cast an spell that deals fire damage, you can have it instead deal radiant damage instead. You also gain fire resistance. At 12th level this becomes fire immunity.

All Consuming Flame

At 15th level, your body has become the only thing keeping the torrent of fire that is your soul from destroying everything around it. When you drop to 0 hit points, make a Charisma saving throw against your own spell save DC. On a failure, you cast fireball centered on yourself, without expending a spell slot. It is cast at a level equal to the highest-level spell slot you can prepare. You can voluntarily fail this saving throw.

Ashes to Ashes

When you reach 20th level, you become wreathed in an aura of pure flame. Any creature that touches you or hits you with a melee attack while within five feet of you takes 1d6 fire or radiant damage (your choice). You still take damage as normal. You can activate or deactivate this aura with a bonus action.

You may also take a action to take necrotic damage equal to half your total hit points. If this damage drops you to 0 hit points, your Flames from Within ability activates as normal. You then make a death saving throw, returning to the number of hit points you had immediately before you activated this ability on a success. If at least one other creature was reduced to 0 HP by the use of this ability, you make the death save with advantage. If you fail this initial death save, you continue to make death saves as normal with no additional benefit.