Comments from the Finger: I've been sitting on this one for a while as part of a different project, but ultimately it works better as a wizard.
School of Diabolism
You have long considered that power is most often profane. Vile fiends, which reside in eternal pits of flame outside the mortal realm, wield power that puts the works of mortal men to shame. Yet, they are unequivocally evil and going so far as to strike a bargain with one is worthy of damnation. Through intense study of obscure summoning and binding rituals, you've reached out to the Lower Planes and have contacted a fiend yourself, not to parlay with, but to command.
By 2nd level, you are well versed in all manner of occult rituals and fiendish summons, and have advantage on Intelligence (Arcana) checks involving them.
At 2nd level, you add the find familiar spell to your spellbook, if it was not there already. When you summon your familiar, you can instead summon an imp which obeys your commands as a familiar does. As a bonus action on your turn, you can command your imp familiar to perform an action or make an attack.
Anchor of Hell
At 6th level, as an action you can select 1 creature you can see within 30 feet to make a Charisma saving throw. On a failed save, for the next minute every foot the creature moves costs 1 extra foot. After using this ability, you must complete a short or long rest before using it again.
By 10th level, you are exceptionally shrewd at infernal negotiations, and have advantage on Charisma (Persuasion) checks made against fiends. Additionally, the time required for you to cast the find familiar spell as a ritual to summon an imp is reduced to 1 action.
Beginning at 14th level, by expending a spell slot of 3rd level or higher, a spell slot of 5th level or higher, and a pint of fresh blood, you can perform a ritual requiring 1 hour of concentration to summon a fiend from the lower planes.
By sacrificing a living, intelligent creature to the fiend, or by sacrificing a great quantity of your own blood to the fiend (reducing your hit points by half your maximum, and reducing your Constitution score by 2 until you complete a long rest) you can gain one of the following benefits for the next 24 hours:
- You can enlist the services of a fiend of challenge 5 or lower for a day.
Roll initiative for the fiend, which has its own turns. The fiend disappears when it drops to 0 hit points or at the end of 24 hours. The fiend is friendly to you and your companions for the duration but otherwise acts according to its alignment. It obeys any verbal commands that you issue to it (no action required by you), but can interpret the command insidiously if proper wording isn't used. If you don’t issue any commands to the fiend, it defends itself from hostile creatures but takes no other actions.
- You can gain resistance to nonmagical bludgeoning, piercing, and slashing damage for the duration.
- When you roll damage for a spell, you can reroll a number of the damage dice up to your Intelligence modifier. You must use the new rolls.
- You can cast any spell of 7th level or lower once in the next 24 hours without expending a spell slot or spell components.
Changelog: 1/25/16: Devil's Advocate added
Form Pact: No spell slots or spell components required to cast pact spell of 7th level or lower
Name Change: Diabolist fits better than Demonologist in a D&D context
Devil's Advocate: Reworded
1/26/16: Form Pact: Can enlist a 'fiend' rather than a devil or demon, to be more inclusive
2/2/16: Form Pact: Maximize damage option changed to be similar to Empowered Spell