Your focus is on the deadly qualities of both natural and unnatural toxins and venoms. Rogues of this archetype are often alchemists, apothecaries, gallipots, physicians and sciolists who relentlessly strive to unlock the secrets of poisons and how they affect the body. Daggers and arrows are just the vehicle to deliver your true weapon: the lethal concoctions of your noxious art.

Venom Soaked

Starting at 3rd level, you are able to lace your weapons with deadly toxins to weaken your enemies. When a creature takes damage from your Sneak Attack feature, you may choose to inflict an equal amount of poison damage instead. You are also able to apply poison to 3 blades/arrows/ammunition with a single action, and an extra one with a bonus action. At level 9 this increases to 5 per action and 3 per bonus action.

Student of Sinister Substances

When you choose this archetype at 3rd level, you gain proficiency in the Medicine skill and poisoner's tool kit if you don't already have it. Your proficiency bonus is doubled for any ability check you make that uses either of those proficiencies. Additionally, the material cost for any poisons made by you is halved and when you harvest poison from the corpse of a creature, you harvest double the amount you would have normally harvested.

Mithridate

Starting at 9th level, your practice and exposure to toxins is so incredible that you have been able to self-administer toxins in minute amounts in order to build up a tolerance. You gain immunity to poison damage and the poisoned condition.

Penetrating Poisons

At 13th level, your study of poisons has become so intense that you are able to create poisons which ignore the natural defense of many creatures. When you deal poison damage to a creature, you may ignore its resistance to that damage. Additionally, no effect may give that creature advantage on saving throws against the poisoned condition which your class features apply to it.

Venomous Virtuoso

At 17th level, you are able to craft poisons so potent that they harm creatures that can ordinarily entirely ignore them. You ignore immunity to poison damage and the poisoned condition when you apply them to a creature as a result of a class feature.