Nightshade

Trained in the art of concocting poisons, Nightshades carry out their goals with precision and efficiency. Whether you learned your craft from natural spirits, a mad mage, or long-forgotten scrolls, Nightshades often prefer to weaken their target themselves before letting others do the dirty work.

Bonus Proficiencies

When you choose this archetype at 3rd level, you gain proficiency with the poisoner’s kit and the herbalism kit. You also gain advantage on any ability checks made to identify compounds with poisonous attributes and the effects of poisons once administered.

Envenom

Your knowledge of poisons and other toxic substances allows use to debilitate your foes in combat, weakening them for your allies. Starting at 3rd level, whenever you hit a creature with an attack where your Sneak Attack feature would apply, you may choose to deal an equal amount of poison or acid damage in lieu of your regular Sneak Attack damage.

Additionally, when you deal poison or acid damage, you can choose to expend one Sneak Attack die and have the creature roll a Constitution saving throw against a save DC equal to 8 + your proficiency bonus + your Intelligence modifier. On a failure, the creature becomes poisoned for 1 minute and gains one of the effects described on the Envenom table below, as your poisons affect each individual differently. The effect gained is determined by a roll of the expended Sneak Attack die. A creature cannot have more than one of the effects on the Envenom table at a time. It may make another saving throw at the end of each of its turns.

d6	Effect
1	The creature cannot regain hit points.
2	The creature moves 5 feet in a direction of its choosing if it can move and its speed is at least 5 feet.
3	The creature must subtract 1d4 from the next saving throw it makes.
4	The creature's speed is reduced by 10 feet.
5	The creature is knocked prone.
6	The creature cannot take reactions.

Once a Sneak Attack die has been expended, it is neither included in future damage rolls when Sneak Attack would apply nor can be used to apply another condition. You regain all expended uses of your Sneak Attack dice whenever you finish a long rest.

Intoxicating Allure

You've refined your concoctions to be able to affect others' perceptions of you. When you reach 9th level, whenever a creature is afflicted by one of your poisons, instead of gaining the benefits from your Envenom feature, you may choose to expend a Sneak Attack die and have the creature roll a Constitution saving throw against the same DC used in your Envenom feature. On a failure, the creature is either charmed or frightened of you (your choice) for a number of minutes equal to 10 times the number roll on your Sneak Attack die. The creature can repeat this saving throw once every 10 minutes.

Mutator of Miasma

Working with chemicals and dangerous substances has become second nature: an extension of yourself. Beginning at 13th level, whenever you obtain a poison not originally made by you, you can change its type over the course of a long rest.

Kiss of Death

It's true that your poisons affect each and every creature differently, but your gifted mind has turned that to your benefit. At 17th level, whenever you expend a Sneak Attack die using your Envenom feature, you can either add a roll of the die to the save DC or choose which additional effect the creature will suffer if they fail. You may use this ability a number of times equal to your Intelligence modifier, and you regain all expended uses when you take a long rest.