Sometimes the spark of magic that fuels a sorcerer comes from a abyssal source that has deeply tainted the soul. Having such a corrupted soul is a sign that your innate magic might come from a distant but powerful familial connection to an infernal being. Perhaps your ancestor was an demon, possessing a mortal and sent to fight in a conquest. Or your birth might align with an ancient prophecy, marking you as a servant of the devils or a chosen vessel of abyssal magic.
An Abyssal Soul, with a natural magnetism, is seen as a threat by some cult’s hierarchies. As an outsider who commands damned power, an Abyssal Soul can undermine an existing order by claiming a direct tie to the infernal

fiendish magic

Your link to the abyss allows you to learn spells from the warlock class. When your Spellcasting feature lets you learn or replace a sorcerer cantrip or a sorcerer spell of 1st level or higher, you can choose the new spell from the warlock spell List or the sorcerer spell list. You must otherwise obey all the restrictions for selecting the spell, and it becomes a sorcerer spell for you.

In addition roll a d10 you learn the following spell based on the result this represents your infernal heritage

Roll/heritage
spell
1/demon - Burning hands
2/Zariel - searing smite
3/dispater - disguise self
4/mammon - tenser’s floating disk
5/belial or fierna - charm person
6/levistus - Armor of Agathys
7/glasya - sleep
8/baalzebul - ray of sickness
9/Mephistopheles - magic missile
10/Asmodeus - hellish rebuke

 

 

abyssal affinity

Starting 1st level the powers of the abyss guide your destiny, should a creature within 60ft of you pass a saving throw or hit yourself or an ally with an attack roll you can choose to subtract 2d4 to the result to possibly change the outcome. Once you use this feature you cannot use it again until you finish a short or long rest

empowered harming

Starting 6th level the abyssal power flowing through you can empower your spell attacks. When you would roll dice to deal damage to an opponent via a spell attack, you can choose to use a sorcery point to reroll any number of those dice once, you can only use this feature once per turn

infernal form

Starting 14th level as a bonus action you can allow your infernal heritage to take over your body, when you do you gain temporary hit points equal to your level in this class while you have these temporary hit points you gain a set of infernal wings giving you a flying speed of 30, you gain advantage on all spell attack rolls you make and you give your opponents disadvantage on saving throws against spell attacks you cast. Once you have used this feature you cannot use it again until you finish a short or long rest

hellish revolt

Starting 18th level you can utilise your infernal heritage to strike down those that harmed you as a reaction when you are hit by an attack that causes you to lose hit points so that your current hit points half or less than your maximum you can cause your infernal blood to assault the enemy that attacked you dealing damage equal to the difference between your current hit points and your hit point maximum in any damage type except for radiant damage. Once you use this feature you cannot use it again until the end of a long rest