You are imbued with the fiery regenerative spirit of the phoenix. You might trace your lineage back to the plane of fire, or perhaps you were born after a ritual involving a phoenix egg. You have a natural affinity and predisposition for fire magic. 

Inferno Magic

Starting at 1st level, whenever you would deal damage with a spell, you may deal fire damage instead of whatever damage type that spell would normally deal.

Regenerative Soul

Whenever you spend one or more hit dice during a short rest, you gain an additional number of hit points equal to your sorcerer level.

Burning Intensity

Starting at 6th level, you gain resistance to fire damage. In addition, whenever you deal fire damage with a spell, you can spend 1 sorcery point to ignore any target's resistance to fire damage, and treat any target's immunity to fire damage as if it was resistance to fire damage instead.

Incandescence

Starting at 6th level, you begin to radiate heat. You are constantly warm to the touch, and you are immune to the harmful conditions of extreme cold weather. Furthermore, as an action, you can glow, shedding bright light in a 20 foot radius, and dim light for an additional 20 feet. You continue to glow this way for up to an hour, or until you spend an action to end the effect. When you reach 18th level, you instead shed bright light in a 60 foot radius, and dim light for an additional 60 feet. 

Fiery Rebirth

Starting at 14th level, when you die, your body explodes, and each creature within 10 feet of you takes fire damage equal to your sorcerer level + your Charisma modifier. In the ashes lies a large ruby, forever hot to the touch, which holds your soul. The gem has AC equal to 10 + your Charisma modifier, and it has hit points equal to your maximum hit points. In a number of days equal to 6 minus your Charisma modifier, if the gem has not been destroyed, it explodes harmlessly, and your body reforms in a flash of fire. If a spell, such as raise dead, has the sole effect of restoring you to life (but not undeath), it can target this gem in place of your body, at which point your body reforms as if the requisite time had passed.

Phoenix Form

Starting at 18th level, you gain immunity to fire damage. You also grow flaming wings and gain a flying speed of 60 feet. In addition, you are perpetually wreathed in flames. Whenever any creature touches you or hits you with a melee attack while within 5 feet of you, you can use your reaction to deal fire damage to it equal to your Charisma modifier.