Base Class: Fighter
Those who walk the path of the Hellfire knight have embraced the fiery passion of battle from within their very souls ,channeling it into their very being as hellish flames that can condemn their foes or be a salvation to those who follow them. Some use it as light to lead others, while others use it as a force of destructive power to rend their foes unto a hellish torrent of flames and blades. The passion and desire they have for battle is known by all for those who walk this form of combat.
Fiery Strikes
Starting at 3rd level, you use a bonus action to imbue your attacks with the heat of battle. All of your attacks deal an additional 1d4 fire damage for 1 minute, you also gain resistance to fire and disease for the duration. The 1d4 is replaced by a 1d6 at 10th level, then replaced by a 1d8 at 14th level, and finally a 1d10 at 18th level. You can use this feature as many times as your proficiency modifier per long rest. Gaining any and all expended uses on a long rest. This feature ends early if killed or knocked unconscious.
Spellcasting
When you reach 3rd level, you augment your martial prowess with the ability to cast spells.
Cantrips
You learn two cantrips of your choice from the Sorcerer spell list.
Spell Slots
The Hellfire Knight Spellcasting table shows how many spell slots you have to cast your sorcerer spells of 1st level and higher. To cast one of these spells, you must expend a slot of the spell's level or higher. You regain all expended spell slots when you finish a long rest.
For example, if you know the 1st-level spell Shield and have a 1st-level and a 2nd-level spell slot available, you can cast Shield using either slot.
Spells Known of 1st Level and Higher
You know three 1st-level sorcerer spells of your choice, two of which you must choose from the evocation or transmutation on the sorcerer spell list.
The Spells Known column of the Eldritch Knight Spellcasting table shows when you learn more wizard spells of 1st level or higher. Each of these spells must be an abjuration or evocation spell of your choice, and must be of a level for which you have spell slots. For instance, when you reach 7th level in this class, you can learn one new spell of 1st or 2nd level.
The spells you learn at 8th, 14th, and 20th level can come from any school of magic.
Whenever you gain a level in this class, you can replace one of the sorcerer spells you know with another spell of your choice from the sorcerer spell list. The new spell must be of a level for which you have spell slots, and it must be an evocation or transmutation spell, unless you're replacing the spell you gained at 3rd, 8th, 14th, or 20th level from any school of magic.
Spellcasting Ability
Charisma is your spellcasting ability for your wizard spells, since you learn your spells through study and memorization. You use your charisma whenever a spell refers to your spellcasting ability. In addition, you use your charisma modifier when setting the saving throw DC for a sorcerer spell you cast and when making an attack roll with one.
Spell save DC = 8 + your proficiency bonus + your Charisma modifier
Spell attack modifier = your proficiency bonus + your Charisma modifier
Fiery Soul
Starting at 7th level when you are reduced to 0 hit points you can instead drop to 1 point. When you use this feature you generate a fiery explosion centered on you that has a radius of 15 feet. All creatures within this radius must make a dexterity saving throw, 8 + your Proficiency + your constitution modifier. On a failed save they take 4d8 fire damage and half as much on a successful save. You can not use this feature again until you finish a long rest.
Burning Bright
Starting at 10th level, the flames inside you emits a light in a 30ft radius that can be emitted from you at will. You can suppress this light in a 30ft radius.
Exalted Fire
Starting at 15th level, you are hot to the touch, and gain a permanent immunity to fire damage. You also gain the ability to cast Heat Metal at will.
Walking Inferno
Your mere presence burns those who come across you. While Fiery Strikes is active, you can increase the firepower of your attacks. After using this feature with your bonus action, for 1 minute, all weapon attacks you make deal 2d10 extra fire damage, ignoring resistances and making those with immunity have resistance instead. This feature ends if Fiery strikes ends early, you are killed, and/or knocked unconscious. This resets after a long rest.
Hellish Supernova
You cause a supernova of fire to burn everything around you. This last a minute, or until your are knocked unconscious or die. last All objects in a 30ft sphere, centered around you, turn to ash, and all creatures must make a dexterity save. On a failed save, the creatures take 10d8 fire damage, or half as much on a successful one while entering, starting within the sphere or end their turn in it. This ignores those with fire resistance and cause those with immunities to fire to become resistant to it instead while affected. This ability resets at dawn.