Blood of the Firebrand

When fire runs through your veins, few things can stand in your way 

Born of Fire

You are immune to fire damage and you know the 'Control Flame' and 'Produce Flame' cantrips; and you may also add your CHA modifier to any spell that deals fire damage. You also have an aura of comfortable warmth with a 5 ft radius (centered on yourself) which you can turn on and off as a bonus action. This negates or lessens any negative effects from cold temperatures you and other creatures within the radius would suffer

Rage of the Firebrand

Starting at level 6, you can add double your proficiency bonus to any STR or CON check or saving throw that you are not already proficient in; OR you can ignite the air around you, causing an explosion centered on yourself. The explosion has a 10 ft. radius and any creature within that radius must make a DEX saving throw (DC is your spellcasting DC). On a failure they take 4d6 fire damage, and half on a successful save. 

Phoenix Flight

Starting at level 14, you gain the ability to fly as action, propelling yourself through the air by shooting flames from your palms. You can not attack while flying, but you leave a 10 ft. long trail of fire in your wake. Any creature caught in this trail must make a DEX saving throw (DC is your spellcasting DC) or take 1d6 fire damage and catches on fire if possible. 

Elemental Form

Starting at level 18, You assume the form of a fire elemental for the Duration. 
Your game Statistics are replaced by the Statistics of the fire elemental, though you retain your Alignment and Intelligence, Wisdom, and Charisma scores You also retain all of your skill and saving throw proficiencies, in addition to gaining those of the fire elemental , If the fire elemental has the same proficiency as you, and the bonus listed in its Statistics is higher than yours, use the fire elemental's bonus in place of yours. You can't use any legendary Actionsor Lair Actions of the new form.
You assume the Hit Points and Hit Dice of the new form. When you revert to your normal, you return to the number of Hit Points you had before you transformed. If you revert as a result of Dropping to 0 Hit Points, any excess damage carries over to your normal form. As long as the excess damage doesn't reduce your normal form to 0 Hit Points, you aren't knocked Unconscious.
You retain the benefit of any features from your class, race, or other source and can use them, provided that your new form is physically capable of doing so. You can't use any Special Senses you have (for example, darkvision) unless your new form also has that sense. You can only speak if the creature can normally speak.
When you transform, you choose whether your Equipment falls to the ground, merges into the new form, or is worn by it. Worn Equipment functions as normal. The DM determines whether it is practical for the new form to wear a piece of Equipment, based on the creature's shape and size. Your Equipment doesn't change shape or size to match the new form, and any Equipment that the new form can't wear must either fall to the ground or merge into your new form. Equipment that merges has no effect in that state.