Serpent Soul

Perhaps you are descendent of a Yuan-Ti, maybe a family member made a pact with a serpentine entity, or it could just be divine intervention by a serpentine god.  Whatever the case, you have reptilian blood in your veins and are able to draw upon the inherent magic at will.  Serpent soul sorcerers can have more reptilian features, but this is not always the case.  While some have forked snake-like tongues others don't, some have reptilian pupils while others retain their race's natural appearance, and others still can have patches of scaley skin.  While none of these appearance changes affect your abilities, consider how reptilian you want to appear as a part of the character's backstory or story in general.  Did Zehir curse/bestow a boon upon you at birth?  Perhaps the Yuan-Ti blood in your veins is just extra potent?  Either way the choice is yours!

Serpent's Tongue

At 1st level you gain proficiency in Deception if you don’t already have it. You also can communicate with any serpentine creature, regardless if it shares a language with you as long as it has 3 intelligence or higher.

Serpent Magic

At 1st level you are resistant to poison damage and are immune to the poisoned condition. You also learn the Poison Spray Cantrip and it doesn’t count against your cantrips known.

Venomous Bite

Starting at 6th level when you make an unarmed strike attack, you can choose to make the attack a melee spell attack biting the target. This bite does 1d6 piercing damage and forces the target to make a constitution saving throw against your spell DC or take 2d12 poison damage or half as much on a success. Additionally you may spend 1 sorcery point to make the strike a ranged spell attack as you spray the venom at your target with a range of 20/60 feet. The damage is still only 2d12 poison damage with no piercing damage and the constitution saving throw is required. Whether you choose to make the attack ranged or melee you may spend an additional sorcery point to inflict the poisoned condition on the target.

Potent Poisons

Starting at level 14 poison damage you deal from spells or your Venomous Bite attack negate resistance to poison damage a target may have and a creature that is immune to poison damage still takes half of the damage. Additionally, as part of your Venomous Bite action or any spell that deals poison damage, you may spend 2 sorcery points to force disadvantage on the saving throw. The poison damage of your venomous bite increases to 3d12.

Perfect Poisoner

At level 18 you are now immune to all poison damage AND the poisoned condition. You’ve learned to bend noxious agents to your will. You may spend 3 sorcery points for one of the following actions:

-Lasting Poison: If you target a creature suffering from the poisoned condition, they take an extra 4d12 poison damage at the start of their next turn unless they succeed on a constitution save against your spell DC, or half as much on a success.
-Enhance Poison: If you target a creature suffering from the poisoned condition, you may choose to inflict them with paralysis for 1 minute if they fail a constitution saving throw against your spell DC. If they fail, they may make another save at their end of their next turn.