Oath of the hellion

Paladin who is known by many names a fire Warden amongst other things

The initial kindling

 Swearing the oath of the hell at, third level ignite something special inside you

 

Searing smite deals an additional die of damage when used on both the initial and subsequent damage rolls

 

You also gain access to the Firebolt cantrip

Aura of flame

Beginning at 7th level the flame that burn inside you have manifested in an aura

You gain resistance to fire damage in any Ally within 10 feet of you does as well

Additionally your aura can nullify protections against Flame another creatures up to 10 ft away. Creatures that are immune to fire become resistant to it and resistance is removed

At level 18 the aura reaches up to 30 ft

Scorched skin

At level 15 what once was a small ember now roars mightier than the wildest of wildfires

You gain immunity to fire damage

Additionally whenever a creature hits you with a melee attack you may use your reaction to cause that creature to take damage equal to double your charisma modifier (minimum 2)

Call forth the Phoenix

At 20th level you can channel the Wrath of the Phoenix

Using your action aspect of the Phoenix to envelop you, for one minute or until you are incapacitated you gain the following benefits

Wings of flame sprout from your back 40-ft fly speed melee weapon attacks dealing additional 2d6 fire damage 

You can cast Firebolt as a bonus action

Can use this feature once before needing a long rest