Adept Poisoner Feat

You specialize in developing poisons, granting you proficiency with poisoner's kits and the following benefits:

Prerequisite: None

• When you create a poison, you can specify a creature type that poison is specifically made for. That poison ignores resistance and immunity to poison damage for that creature.
• You can apply poison to a weapon or piece of ammunition as a bonus action, instead of an action.
• During a long rest, you can perform 1 hour of work using a poisoner's kit to create a number of doses of potent poison equal to your proficiency bonus, which last until you apply them to a weapon or finish your next long rest. Once applied to a weapon or piece of ammunition, the poison retains its potency for 1 minute or until you hit with the weapon or ammunition. When a creature takes damage from the coated weapon or ammunition, that creature must succeed on a Constitution saving throw (DC equal to 8 + twice your proficiency bonus) or take 1d8 poison damage and become poisoned until the end of your turn. On a success, they take half as much damage and aren't poisoned.

When you use this feature to create a poison, you can expend 15gp per dose of poison to create a more deadly poison. When you do so, creatures that fail their Constitution saving throw against it take an extra 1d8 poison damage.
Source: KCCC, page 124