There are known to be many different sources of magic throughout the multiverse, and a sorcerer can conceivably draw their power from any of them. Sometimes, a sorcerer's power is born from the fiery blood of some demon lineage connected to themselves. Drawing power from the foulest depths of the Nine Hells, these sorcerers are not inherinetly evil, but those that aren't must constantly fight with their own instincts to not become corrupted.

Clearly however, a sorcerer to be known with this ancestry is often alienated amongst their peers, and find it hard to find allies that trust them for who they are.

Infernal Instinct

Starting at 1st level, your demon blood can start amplifying your abilties. Whenever you make an ability check or saving throw that uses STR or CHA, you may choose to gain expertise with the roll, adding your ability modifier and twice your profiency bonus. You may choose to use this ability after you have seen the roll, but the DM has not resolved the outcome. Once you use this feature, you can't use it again until you finish a short or long rest.

Burning Hate

Starting at 6th level, your ways of drawing the life from your enemies are bolstered by your ancestry. Whenever you cast a spell targeting a single creature that deals fire or necrotic damage, you may spend a number of sorcery points equal to the level of the spell to immediately double the damage. You may decide to do this before or after the damage dice have been rolled, but not after the results have been determined by the DM. This feature may not be used in conjunction with spells that require concentration.

Body From Below

At 14th level, your demonic blood grants you more mastery of your own form. You now know the alter self spell, if you didn't know it already. This spell does not count against the number of known spells you have. Additionally, your version of the spell grants you additional options of your choice, though you must still comply with the rules of the spell:

Demon Eyes: Your eyes turn a malignant yellow colour. You gain darkvision out to a distance of 120 feet, and you are able to see through magical darkness

Nightmare Wings: Bat-like wings sprout forth from your back. You gain a flying speed equal to your walking speed.

Unholy Assistance

At 18th level, your mastery of your legacy has granted you power over some of the beings that live below. You may spend 7 sorcery points as an action on your turn to summon one of the following creatures: horned devil, bone devil, erinyes or chain devil. The creature is friendly to you and your allies, and will aid you in a fight where it is able to. Roll for initiative for the creature, and it will act on its own turn. You do not have fine control over the creature, however it will consider what you decide to tell it. The creature returns to its own plane of existence if it drops to zero hit points. The creature has no obligation to stay with you, however it will likely do so while you are not doing anything harmful towards it. If you or any of your companions harm or even offend the creature, not only will it return to its own plane of existence but you will also be unable to use this feature for 7 days.

Once you use this feature, you may not use it again until you have finished a long rest.