Corrupted Scholar

Few arcane colleges specialize in researching the Abyssal planes and those that inhabit them, for fear their corruption may spill over into the material plane and sew chaos and destruction across the land. Some scholars disregarded this fear and peered long into the Abyss, not knowing that something had peered back until the stain of corruption had already left its mark on their soul. As the corruption grows stronger, so too does their ability to wield the powers of the Abyss. 

Those few mages who have come to wield this power find themselves changed by the darkness of the Abyss, able to command lesser demons to do their bidding and finding their body more and more changed by the day. Some live long enough to make great strides into the research of demon kind and the nature of the corruption that mars them, while others are easily mistaken for demons themselves and slain by either their former colleagues or mercenaries seeking fame. 

Demonic Corruption

At 2nd level, the stain of the Abyss has begun to change you inside and out, marring your physical form with black scarring that cannot seem to be healed by magic or medicine. This scarring gives you advantage on Intimidation checks and Charisma checks made to interact with demons or their various cults, but disadvantage on Persuasion checks made on interactions with everyone else. 

At 6th level, your hands twist into terrible claws, giving you a Claw attack as a natural weapon. This attack deals 1d6 Slashing damage and is considered magical for the purpose of bypassing resistances. These claws make it difficult for you to wield man-made weapons, giving you disadvantage on attacks made with manufactured weapons. You are proficient in attacks made with this weapon and it uses your Intelligence modifier instead than your Strength modifier. 

Abyssal Commander

Starting at 2nd level, you can harness the Abyssal energies that have stained your soul to summon 2d4 + your spellcasting ability modifier Manes (minimum of 3) as an action. Demons summoned using this feature are loyal to the caster, can communicate telepathically with them, and will follow commands to the best of their ability. The demons can be commanded as a group as an action or as individuals as a bonus action and share initiative with the caster. If not given any commands they will not act, instead staying within 5ft of the caster. If a hostile creature makes a melee attack against the caster while one of these demons are within 5ft, they will force the creature to attack them instead. When acting as a group, the demons' collective AC is equal to the average AC of the group minus the average attack modifier.

Only one group of Demons can be summoned using this feature and will remain until their hit points reach 0 or are dismissed as an action. 

The amount of Manes you can summon doubles at 6th level and triples at 10th level. 

The Black Page

Starting at 6th level, a new, pitch black, page is added to your spellbook with instructions penned in Abyssal in blood. You gain proficiency in the Abyssal language if you did not already have it and the ability to cast Summon Lesser Demons without material components if you did not already have the spell. This spell does not count against your prepared Wizard spells. Demons summoned by this spell are still hostile to all creatures, including you. 

Empowering Corruption

Beginning at 10th level, any demons summoned by you hit point maximum is increased by an amount equal to your Wizard level. Additionally, all demons under your command add your proficiency bonus to their weapon damage rolls. 

False Demon Lord

At 14th level, you've been exposed to the corruption of the Abyss for so long that you have become indistinguishable from a demon. Any demons summoned by you recognize you as their Lord and follow your orders without question, even if that order would put their life in danger. Additionally, you can force your will upon any demon you encounter to force them into your servitude, forcing them to make a Wisdom saving throw against your Spell Save DC to resist you. A demon with an Intelligence score of 10 or higher will not be affected by this feature, as they know of true Demon Lords stronger than you. 

If you successfully force a demon to submit to your will they will follow your orders until you use this feature in this way again. If the demon succeeds the saving throw you cannot use this feature on them again until you finish a long rest.