Way of the raging star

The monks known as the raging stars, have learned to harness their ki energy as fuel for the fiery energy contained within them. On the battlefield they are seen as a roaring mass of fire that crashes through the ranks of their enemies, leaving nothing but ashes and embers.

Combustion

At 3rd level, as an action, you can spend 1 ki point to unleash the celestial energy contained within you, causing your body to temporarily enter a state of molten hot plasma.

Until the end of your turn, you do not provoke attacks of opportunity, you ignore difficult terrain and you are able to move through another creature's space without squeezing. You are immune to the grappled and restrained conditions as well as immune to fire damage. However, you become susceptible to water. For every 5 feet you move in water, or for every gallon of water splashed on you, you take 1 cold damage.

In addition, while this feature is active, whenever you move through another creature's space it must make a dexterity saving throw against your ki save DC or take fire damage equal to four rolls of your martial arts damage die or half as much damage on a successful save. A creature cannot be affected by this feature more than once per turn.

Finally, you shed bright red, orange or blue light in a 10 feet radius, and dim light for another 10 feet. While your combustion feature is active you cannot be invisible.

Ignite

At 6th level, whenever you deal fire damage with your combustion feature to a creature, it catches on fire. For 1 minute, or until a creature takes an action to douse the fire, the target takes fire damage equal to a roll of your martial arts die, at the start of each of its turns.

A creature cannot be affected by multiple instances of 'Ignite' at the same time.

Cauterize

At 11th level, you can spend 2 ki points to have your monk features ignore any fire resistances and fire immunities on enemy creatures until the end of your next turn.

Roaring flame

At 17th level, you can choose to prolong the duration of your combustion feature to 1 minute, being able to end its duration early as a reaction. Additionally, while your combustion feature is active, you gain a flying speed equal to your normal speed and all your unarmed strikes deal fire damage instead of bludgeoning damage.

Rules made by Blackflight

Image source: http://www.theblackguywhotips.com/2016/08/31/1275-she-was-lit/fire-girl/