Pyromaniac

This sorcerer specialising in fire and burning and flame and incinerating whatever causes them difficulties. They have a tendency to cause a lot of collateral damage.

Unstable Bursts

Your power is unstable, causing fire spells and attacks to burst off and creates blazes of flame nearby.

Whenever you hit a spell attack or a target fails a saving throw against one of your spells that deals fire damage, roll a d8. The 5x5 ft tile adjacent to the target dictated by the result (1 being north, going clockwise) is set ablaze with magical fire. If the space is blocked off by a wall or other full surface, then the flame rebounds off it and the dice is rolled again.

Any creatures within the space must roll a Dexterity saving throw and take 2d4 fire damage (increasing to 3d4 at 7th level, 4d4 at 14th level, and 5d4 at 20th level), halved on a success. The first time a creature enters the fire on their turn or whenever one ends its turn inside, it makes the same check, taking the equivalent damage.

A spell that damages multiple targets can spawn up to two flames (three at 9th level and four at 15th level) split randomly between targets (max one per target). A fire can spread if there is sufficient fuel to burn, but without any fuel the fires last for two turns before extinguishing.

Fire Weaver

Starting at 6th level, you can use a bonus action and a sorcery point to move any number of Bursts of Flame within 30ft of you up to 5ft in any direction. The flames need to remain on the ground or some other relatively unmoving surface. Creatures on the spaces they move to take damage as if they have entered the fire.

You also gain resistance to fire damage.

Consuming Flames

At 14th level, you gain slightly more control over your bursts. After you roll to determine an Unstable Burst's location, you may choose to reroll the die and then keep the second result.

You are also able to spew forth more flames than before. Whenever you cast a fire spell you may choose to create an unstable burst in one of the spaces adjacent to you as determined by the d8 in addition to any created by the Unstable Burst feature.

Pyreborn

Beginning at 18th level, you have been consumed by the fire and have consumed it. Some Pyreborn have cracked, seared skin with glowing embers in the gaps, others have fiery, ethereal hair that waves like tongues of fire. Still others look as a hybrid of flesh and elemental, with searing flames for eyes and red hot skin.

You have immunity to fire damage and your unstable bursts can last three turns without fuel. In addition, whenever you would take fire damage, instead gain 1d12 temporary hit points.