Path of the Ember Heart

When the body can no longer contain the furnace that burns within the chests of these barbarians, it is unleashed upon their foes in an explosive inferno of violence. Woe to those who stand too close to this sweltering hearth as the crazed agony the barbarian himself feels will soon be shared.

Ignite

Starting when you choose this path at 3rd level, you ignite when you rage. You gain resistance to fire and cold damage, deal 1d4 fire damage with each melee weapon attack, and enemies reduced to 0 HP by a melee weapon attack grant you 1d4 + your rage damage bonus in temporary HP. At the end of each of your turns while ignited, you must endure 1d4 fire damage. If you do not receive at least 1 fire damage at the end of each of your turns, your ignition will end. You cannot drop below 1 HP from this fire damage. 

Your fiery spirit broils such that you may rage as a reaction.

Desiccate

Beginning at 6th level, after achieving a hit on a creature with a melee weapon attack while raging, you may desiccate that creature, lowering its fire defense. That creature is stripped of their fire resistance and if the creature is not resistant to fire damage, they are now vulnerable to fire damage until the end of your next turn. You may use this feature a number of times equal to your proficiency bonus per long rest. 

Additionally, anything considered kindling will catch fire after 1 minute in your grasp.

Gasping on Fumes

Beginning at 10th level, you fall to your knees in a transformative immolation. Your eyes turn to glowing coals, granting you blindsight out to 60 ft, and your voice sounds as though a kiln roars at the back of your throat, granting you proficiency in intimidation and persuasion, or expertise if you already do. You can no longer suffocate due to smoke, and you gain resistance to the damage of any cloud or gas like spell or trap. 

Your body is like a living oven - you are unbearable to the touch and creatures grappled by you receive 1d4 fire damage at the end of each of their turns while grappled.

Heap of Ashes

Starting at 14th level, due to your now extremely volatile nature, you may spontaneously combust while raging. At the beginning of each of your turns while raging, you must now roll a 1d4; on a 4, you combust, dealing 1d10 fire damage to yourself. Enemy creatures within a 30 ft. radius around you must succeed on a dexterity saving throw (DC equal to 8 + your proficiency bonus + your constitution modifier) or suffer the effects of desiccation and receive 1d10 fire damage at the start of each of their turns until it's doused with an action, which will also end this instance of desiccation if performed. You cannot fall below 1 HP from spontaneous combustion. Allies caught in the blast instead inflict 1d10 fire damage on their next hit with an attack roll.

Lastly, desiccation now removes fire immunity, making the creature only resistant to fire damage instead.