My attempt to extend the Hellfire Warlock. Inspiration was taken from SirPercival's Lens Mage PrC
Hellfire Warlock HD: d6
Level BAB Fort Ref Will Special
1 +1 +0 +0 +2 Hellfire Blast; Invoking
2 +2 +0 +0 +3 Hellfire Infusion
3 +3 +1 +1 +3 Hellfire Shield
4 +4 +1 +1 +4 Concussive Blast
5 +5 +1 +1 +4 Hellfire Infusion
6 +6 +2 +2 +5 Explosive Invocation
Skill Points: 4+int
Bluff; Concentration; Disguise; Diplomacy; Intimidate; Knowledge (arcana); Knowledge (religion); Knowledge (the planes); Spellcraft; Use Magic Device
Hellfire Blast (Sp): Whenever you use your eldritch blast ability, you can change your eldritch blast into a hell fire blast. A hellfire blast deals your normal eldritch blast damage plus an extra 2d6 points of damage per class level. If your blast hits multiple targets (for example, the eldritch chain or eldritch cone blast shape invocations), each target takes the extra damage. This damage is untyped. Each time you use this ability, you take 1 point of Constitution damage. Because the diabolical forces behind the power of hellfire demand part of your essence in exchange for this granted power, if you do not have a Constitution score or are somehow immune to Constitution damage, you cannot use this ability.
Invoking: At each level, you gain new invocations known, increased damage with eldritch blast, and an increase in invoker level as if you had also gained a level in the warlock class. You do not, however, gain any other benefit a character of that class would have gained.
Hellfire Infusion (Su): Starting at 2nd level, you can infuse magic items that you wield with the power of hellfire. Whenever you use a charged magic item (such as a wand or a staff ), you can apply one of the following metamagic effects to your next use of the item: empower, enlarge, widen, or energy substitution. At 5th level you can also apply extend, maximize, or energy admixture.
Concussive Blast: At 4th level you are able to focus your Hellfire blast into a near solid ray, knocking foes back. On a successful hit with Hellfire Blast you can initiate a bullrush as a free action, with a Strength modifier equal to your Hellfire Warlock's class level plus his Charisma modifier.
Explosive Invocation: Upon reaching 6th level, a Hellfire Warlockâs master is unparalleled. A number of times per day equal to his Charisma modifier, he may make an attack with his Hellfire Blast as a full-round action and apply one eldricht essence of each grade he knows to that attack. He may apply one blast shape essence to that attack if he chooses, but it remains a full-round action. Any creature affected by the Explosive Invocation must save against each eldricht essence individually.
