Toxic Master

You were born to poison.  probably sickly at birth, catching illness sickly.  Few people imagined much would come of you.  But power was dormant in you.  Some whisper of the power of green and copper dragons, but your power is more than that.  More likely you were born in a land subjected to some sort of blight, and that taint remains in you. 

Poison In Your Vains

Starting at 1st level, you have resistance to poison damage and have advantage against constitution saving throws for the poisoned condition.  You may also add your Charisma Modifier to your constitution saving throws against the poisoned condition.

Poison In Your Skin

Whenever you are struck by an unarmed attack or grappled, the attacker takes a number of d6 poison damage equal to your Charisma Modifier. This has no effect on constructs or undead.

The damage increases at level 6 to 2d6, at level 10 to 3d6, and level 14 to 4d6.

Poison Attunment

You gain immunity to poison damage and the poisoned condition.

Further you can secrete your poison at will. All of your weapons are considered poisoned. During a short rest you can take allies weapons to poison them as well. In addition to their normal damage, they deal a number of d4 equal to your Charisma Modifier.

Miasmic Cloud

At 6th level, as an action you may spend 2 sorcery points to create a cloud of poison gas around you. Any enemy who comes within 20 ft of you, or starts it turn in that radius, must make a constitution saving throw against your spell save DC, or suffer a number of D6 equal to your Charisma level.

You may use this a number of times per day equal to your spell casting modifier.

This radius increases to 40ft at level 10, and 60ft at level 14.

Acrid Casting

At 14th level, you gain the ability to weave your poison into your spells. If you cast a spell using a spell-slot of level 1 or higher and it requires you to roll dice to determine damage, you may spend one sorcery point per spell slot level to change all the damage to poison damage instead. You may do this a number of times per short rest equal to your Charisma Level.

If a spell would already deal poison damage, you may spend sorcery points to add extra die to damage rolls up to your poison level. You may do this once per long rest.

Corrupted Biology

Starting at 18th level, you may use your Miasmic Cloud feature an unlimited number of times per day.

If you are hit with an attack that would deal poison damage to you, you may instead regain the poison damage as HP, or 1/4 of it as sorcery points.
If you hit a creature with an attack that deals poison damage you are able to regain the damage dealt as HP, or 1/4 of it as sorcery points. This can be done as many times as your Charisma Modifier per long rest.