Beginning at 1st level, you have resistance to poison damage and advantage on saves against poison.
Blow Chunks
Also at 1st level, you learn the poison spray cantrip. You can cast this without components by vomiting this vile sludge.
A Way of Something Like Life
At level 6 you are immune to the Poisoned condition. Additionally, you have advantage on saves against necrotic damage.
Death in the Blood
At level 14, whenever you take damage, you may bleed buckets as a reaction. Each creature within 5' of you must make a Constitution saving throw or suffer the Poisoned condition. Additionally, you have resistance against necrotic damage.
Walking Wasteland
At level 18 you may spend 6 Sorcery Points to compel a Constitution saving throw from any target you touch: at a failure, the target is Poisoned and drops to 0 HP.