Path of the Crimson Lotus

 Blood boiler, a phenomenon where individuals honed their strong emotion into a certain threshold where they cause their body to emit heat. Barbarians who utilize this phenomenon allow them to channel their rage into an embodiment of fire.   

Practitioner of the Crimson Lotus

As a part of your training within the Crimson Lotus monestary, you gain a better understanding of your body, allowing you to fight with your unarmed strikes and channeling your rage into damaging fire.

Starting at 3rd level, you gain proficiency on Dexterity saving throws. Your unarmed strikes damage is now a D4 plus strength modifier. Additionally while you are raging, your unarmed strikes and weapon attacks instead become fire damage. The damage die is changed as you level up, 1D6 at 5th, 1D8 at 11th, and 1D10 at 17th.

Sanguine Fire

With better training of the Blood Boiling phenomenon, you can create a burst of fire at the cost of harming oneself.

Starting at 6th level while raging, when you hit with a melee attack that deals fire damage, you may expend a barbarian hit dice to deal an additional 1D12 fire damage. You then are dealt radiant damage equal to half of the additional fire damage dealt rounded up.

Blessing of Flame

Although your rage is an all consuming fire, there is a calmness within that allow the fire to become a protective shield.

Starting at 10th level when you rage, you may choose to gain temporary hit points equal to half your maximum hit points rounded up, you may only do this once per short/long rest. When a target hits you with a melee attack while you have temporary hit points granted by this feature, they take fire damage equal to the damage dealt to you. 

Enlighten Fire

Your burning rage became so potent that it can bypass certain defenses against fire and more uses of your Sanguine Fire at an even greater cost. 

Starting at 14th level when you hit with an attack using your Sanguine Fire feature, that attack ignores resistance to fire damage and deals half damage to targets with immunity to fire damage as if they were instead resistance to fire damage. Additionally when you have no hit dice to use your Sanguine Fire feature, you may still use the Sanguine Fire at the cost of taking double the damage from the recoil radiant damage.