Demonic Sorcery

 Your innate magic stems from the twisted essence of a demon. Perhaps one of your ancestors made a pact with a demon lord, or your bloodline was forever altered by exposure to the Abyss. Regardless of the cause, the infernal corruption manifests in you as volatile power, destructive force, and a terrifying presence.

Level 3: Demonic Attunement

Your demonic nature bleeds into your body and magic.

Abyssal Resistance: You gain resistance to fire and poison damage, additionally you have advantage on saving throws against being poisoned.

Demonic Tongue: You can speak, read, and write Abyssal. In addition, when you speak in Abyssal, your voice echoes with unsettling undertones.

Level 3: Demonic Spells

When you reach a Sorcerer level specified in the Demonic Spells table, you thereafter always have the listed spells prepared.

Demonic Spells

Sorcerer Level	Spells
3	Heat Metal, Hellish Rebuke
5	Silence, Feign Death
7	Blight, Bestow Curse
9	Wall of Fire, Summon Fiend

Level 6: Infernal Resilience

At 6th level the abyssal corruption has strengthened your body.

 While you aren’t wearing armor, your base Armor Class equals 10 plus your DEX and CHA modifiers. Additionally, if your Strength score is lower than 12, it increases to 12. If your Strength score is already 12 or higher, you gain advantage on Strength checks and your carrying capacity doubles to reflect your demonic fortitude.

Level 14: Demonic Possession

At 14th level, your demonic nature fully manifests, granting you the ability to leave your body behind and possess others.

 As a bonus action, you can leave your body in the form of a cloud of black mist, leaving your original body unconscious and helpless. While in this form, you are intangible, can hover up to 30 feet per round, and can pass through small cracks and openings, though you cannot pass through magical barriers, solid surfaces or running water. You can remain in this form for up to 1 minute or until you choose to possess a creature. You may attempt to possess a creature within 5 feet that is either unconscious, dead, or has a CR lower than your sorcerer level. If the target is alive or unconscious then the target must succeed on a Charisma saving throw against your spell save DC or be possessed. While possessing a creature, you use its physical stats, but retain your mental stats, class features, and spellcasting. The possession ends if the host body is reduced to 0 hit points, if you choose to leave as a bonus action, or if you're forcibly removed by effects such as Dispel Evil and Good or Hallow. If the possession ends and your original body is still intact, you return to it. If not, you fall unconscious in mist form. Reviving 1D6 days later in hell, from there you make a new character because this one is now in hell becoming a proper demon. However, this comes at a cost as you are now permanently vulnerable to radiant damage.

 Additionally, if your Strength score is lower than 14, it increases to 14. If your Strength score is already 14 or higher, then this part doesn't matter. This is to reflect your now marginally increased demonic fortitude.

Level 18: Abyssal Fortitude

 At 18th level your demonic nature has awarded you with incredible fortitude, you have advantage on Wisdom and Charisma saving throws. In addition to that, whenever you spend Sorcery Points to cast a spell or use a Metamagic option, you gain a number of temporary hit points equal to 2d8 + your sorcerer Level + your CHA modifier for one hour. Temporary hit points from this feature do not stack.

 And to save you all the math for the temporary hit points, at minimum (assuming you have a 20 in charisma) you'd get 25 temporary hit points and at maximum you'd get 39 temporary hit points. That seems like a lot but it really isn't at that level.