Corrupt Fiend Bloodline

Many races consort with dark powers. Corrupted bloodlines often happen when a newborn is promised as payment for a dark deal. Maybe one of your parents was a powerful warlock. Or you may have come into contact with a powerful miasma from the lower planes, permanently altering you and granting you magical skills. 

Corrupted Magic

Your corrupted influence 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.

Additionally, at 1st level, you learn the eldritch blast cantrip. It counts as a sorcerer cantrip for you, but it does not count against the number of cantrips known.

Devil's Charm

1st level Corrupt Fiend Bloodline feature

You innately come by an ability to speak and influence others. At first level, you gain expertise in the deception and persuasion skills.

At third level, you may spend a sorcery point to cast charm person. If cast in this way, the target does not know they were charmed by you. Once you use this feature, you must finish a long rest before using it again.

Infernal Constitution

6th level Corrupt Fiend Bloodline feature 

By level six, you begin to inherit the resistances of denizens from the hells. Gain resistance to cold, fire, lightning, and poison damage.

Additionally, you gain immunity to the poisoned condition. 

Pit of Dispair

6th level Corrupt Fiend Bloodline feature

By level 6, you learn that your very existence twists the delicate thread of hope into knots.

Whenever you hit a creature, or a creature is affected by one of your warlock spells, you may spend two sorcery points to mark that creature. At the start of that creature's turn, it must make a Wisdom saving throw against your spell save DC or be overcome by dispair. All of its ability checks, attack rolls, and saving throws take a 1d6 penalty,  and it may not benefit from advantage until the start of its next turn. 

The mark lasts for 1 minute, until you lose concentration as though concentrating on a spell, or you become incapacitated. 

You may use this feature a number of times equal to your Charisma modifier per long rest. 

Hellish Form

14th level Corrupt Fiend Bloodline feature 

The fiend inside of you grows, and yearns for release. As a bonus action, you can spend 1 or more sorcery points to magically transform your body for 10 minutes. For each sorcery point you spend, you can gain one of the following benefits of your choice, the effects of which last until the transformation ends:

• A creature within 30 feet of you must make a Charisma save against your spell save DC or be charmed by you. This lasts until your form ends, or it receives damage of any kind.
• You gain advantage on saving throws against spells and other magical effects. 
• You may add your Charisma modifier to the damage of your spells.
• You may hurl magical flames. Make a ranged spell attack against a creature you can see within 30 feet as an action. On a hit, the target takes 1d8 fire damage, ignoring resistances and immunities. At the start of that creatures turns, it must succeed on a Constitution saving throw or take an additional 1d8 fire damage. On a success the effect ends.

Heretical Foundry

18th level Corrupt Fiend Bloodline feature

If you would drop to 0 hit points because of an attack, you may instead drop to 1 hit point and teleport as a reaction up to 30 feet away to an unoccupied space you can see. Every creature within 15 feet of your original location must make a Dexterity save against your spell save DC or take 4d6 fire damage and 4d6 lightning damage, taking half as much on a success. 

You may do this once per day, unless you spend 7 sorcery points to use it again.