Hellfire warlock

A Hellfire Warlock is able to enhance the power of their eldritch blasts by harnessing hellfire, a mysterious magical energy found in the Nine Hells. They often gain this power by interacting with the Baatezu, summoning them in order to make infernal contracts or forcibly capturing and interrogating them.

Abilities
Hellfire Blast: Whenever a hellfire warlock unleashes an eldritch blast, they have the option of converting it into a 'hellfire blast'. The hellfire blast inflicts greater damage than a standard blast, but drains a portion of the caster's lifeforce in exchange. The extra damage inflicted is not fire damage; hellfire burns hotter than any fire normally found on the Prime Material Plane. A warlock cannot utilize hellfire blasts if they are immune to constitution damage.

Hellfire Shield: The hellfire warlock may surround themselves with a shield formed from hellfire. The shield provides no protection, but will launch hellfire blasts at any opponent who moves too close to the warlock. The warlock's lifeforce will be drained whenever the shield launches a hellfire blast, and the shield cannot be utilized if the warlock is immune to constitution damage.

Resistance to fire: A hellfire warlock is able to resist the effects of fire weapons and spells, particularly if they already have some form of fire resistance from their studies as a warlock.