Fire Elemental Vessel

Your body or soul houses a fire elemental, of what strength or magnitude you are unsure, but as you grow so does the flame that now exists inside you. The essence of the fire elemental does not just grant some control over the fire but mutates and empowers even your physical essence.

Primordial Essence

Starting at 1st level your character gains dark vision up to 60ft, or if they already have dark vision it is further enhanced by 30ft, additionaly with this dark vision you see in hues of red and orange. As well as this you learn Primordial, while you may not understand where this knowledge came from or even be aware that you do know it, you understand it clearly and can speak it fluently.

Further more as you are physically one with the fire elemental you are emboldened by fire, gaining resistance to fire damage and immunity to the extreme cold weather conditions, you always seem to dry faster than others and people tend to crowd around you...

Essence of Flame

Your body has changed almost having a firey body that lies underneath or in tandum with your regular body, granting you some degree of extra flexibility amongst other things.

From 6th level onward you can expend sorcery points to unleash your firey body in certain ways. For 2 sorcery points you can unleash a wave of fire as a bonus action, this wave is 15ft in length and 10ft in width and does damage equal to your sorcerer level, you can additionally expend a further 2 sorcery points to increase the range to 30ft along and 10ft across.

The Comfort of Fire

From 6th level onwards as a bonus action you can absorb a measure of flame, in a 60ft radius, into your body. You can snuff out all the candles in that area or a medium sized bonfires worth of flame, when you do this you regain a sorcery point or gain an additional sorcery point, additonally you gain temporary hp equal to your charisma modifier.

Fires Form

Starting at 14th level your form can move and stretch like that of a fire elemental, even going so far as to be able to summon fire to the surface.

You are able to fit and move through gabs and spaces as small as 1", you must finish your move in a free space or take 1D10 bludgeoning damage and be unable to take any action other than a reaction until you are in a free space. Aditionally you are able to bring the fire to the surface of your skin, as a reaction to a melee attack against yourself within 5 ft of you, you can make the target take 1D10 fire damage. As well as this as a bonus action you can shed bright light 30ft from yourself and dimlight an additonal 30ft, it is a free action to dismiss the light.

At this level your fire resistance has evolved to fire immunity.

Elder Elemental

Starting at 18th level you can expend 6 Sorcery Points to Alter your form and grant further power.

When you do this you change and take on the appearence of a large grand fire elemental, in this from you grow to size large, have a 50 ft movement and gain a number of temporary hp equal to 3 times your sorcerer level.

While in this form you have resistance to all non magical attacks and have advantage on saving throws against spells and other magical effects.

Additionally while in this form you ignore fire resitance and treat fire immunity as fire resistance