School of Demonology

Weather it is a fascination with the demonic outer planes, a thirst for forbidden power or a desire to assert the dominance of your will over that of demons and devils, you have dedicated your life to studying these dangerous creatures.

Wizards that pursue the school of demonology range from the deranged to the desperate. They could be fascinated by forbidden knowledge, tempted by the possibility of greater powers, or simply unwilling to recognize the very real danger that comes from dealing with such creatures. Whatever the reason may be, demonologists rarely age well, if they get to live to an old age at all. 

Student Of Fiendish Lore

At 2nd level, Your studies of fiends and their history grant you a better grasp of the languages they speak. You gain proficiency in the Abyssal and Infernal languages, if you did not already know them.

In addition, your proficiency bonus is doubled for intelligence (Arcana, history or religion) checks to recall information regarding demons and devils. 

Fiendish Lacky

At 2nd level, you make your first successful attempt at placing an extra planar creature under your control. You add the find familiar spell to your spellbook if it is not there already. When you cast find familiar, you can choose an imp or quasit as your familiar. If you do, you may use a bonus action to command your familiar to make an attack.

When you conjure an imp or quasit using this spell, you may choose to have your hit point maximum reduced by 1d4 until you complete 1d4 long rests, instead of providing the material components for the spell. If you cast this spell using this method while your hit point maximum is already reduced, the hit point reduction stacks, and the long rest counter resets to the new roll (if your hp is reduced by 2 for two long rests, and you use this feature again after one long rest - rolling a 3 on the d4 - your hp is now reduced by 5 until you complete 3 long rests).

Demon Wrangler

At 6th level, you add the summon lesser demons spell to your spellbook if it is not there already. When you cast summon lesser demons you may choose the option from the demon summoning table, rather than roll for it.

When you cast the spell and on each of your turns thereafter, you can issue a verbal command to the demons (requiring no action on your part), telling them what they must do on their next turn. If you issue no command, they spends their turn attacking any creature within reach that has attacked them.

At the end of each of the demon’s turns, they make a Charisma saving throw against your spell save DC. On a failed save, the demons continue to obey you. On a successful save, your control of the demons ends for the rest of the duration, and the demons spend their turns pursuing and attacking the nearest non-demons to the best of their ability. If you stop concentrating on the spell before it reaches its full duration, uncontrolled demons don't disappear for 1d6 rounds if they still have hit points.

In addition, any fiends you conjure deal additional force damage equal to your Intelligence modifier with their first attack that hits each turn. 

Abyssal Markings

At 10th level, you perform an 8 hour long ritual to ward yourself against fiends, and increase your powers of control over them. Mixing the blood of demons or devils with rare powders and inks, you tattoo your body with symbols that weaken the resolve of fiends you summon. 

When you summon a fiend with a CR that is equal to a third of your level in this class(round down) or lower, they have disadvantage on their saves to break free from your control. 

In addition, the first time a fiend you summoned attempts to attack you, it must make a wisdom save against your spell save DC. On a fail, the fiend attacks the nearest target that is not you. If there are no targets in range, the fiend spends its next turn getting as close as it can to the nearest viable target. If there are no targets in sight, the fiend looses the rest of its current turn.

Finally, if you lose concentration on a conjuration spell that summons any number of fiends, you may choose to have the fiends linger before disappearing, for a number of rounds equal to your Intelligence modifier, instead of following the normal rules for losing concentration on that spell. You must still follow any normal rules for maintaining or losing control of the fiends if the spell specifies any such rules, and you take 1d4 necrotic damage at the start of each of your turns while the fiends are still conjured in this way.

Hell-forged Will

At 14th level, your experience with demonic forces has taught you how fiends think and, more importantly, what they fear. Your sheer force of will can be enough to crush a fiends resistance to your control. 

You have advantage on Charisma checks against fiends.
In addition, if a fiend you summoned fails a total of three saves to break free from your control, it loses the ability to make additional saves to break free in this way for the duration of the spell that summoned them. The fiend stays under your control for the reminder of the spell, until it drops to 0 hit points, or until dismissed by you, at which point it returns to its plain of origin.