You have gained more knowledge about poisonous substances and found ways to apply them in different ways.

You are able to distinguish dangerous toxins and capable of using them without suffering their effects.

Basic Toxilogy

When you choose this archetype at 3rd level, you gain proficiency in Alchemist Tools and the Medicine skill if you don’t already have it. Your proficiency bonus is doubled for any ability check you make that uses either of those proficiencies.

In addition you gain advantage on attack rolls against creatures that are Poisoned.

Toxic Cloud

At 3rd level, as a bonus action you create a 10-foot-radius Sphere of poisonous, yellow-green fog for one minute with a range of 30ft. The fog spreads around corners. It lasts for the duration or until strong wind disperses the fog, dispersing the Toxic Cloud. Any creature that enters or starts its turn in that area must succeed on a DC (8 + Wisdom modifier + Proficiency) Constitution saving throw or be Poisoned for one minute. Creatures are affected even if they hold their breath or don’t need to breathe. A creature affected by this makes another Constitution saving throw at the end of its turn. On a successful save, the effect ends for it. You are not affected by your own Toxic Cloud.

You can use this feature a number of times equal to your Proficiency bonus.

Venomous Knowledge

By 9th level, Your body is used to daily exposures of toxins and has developed a resistance to toxic components other then your own.

You  are resistant to Poison damage and have advantage on save rolls to the Poisoned condition. In addition your weapons are now coated in your own trademark toxins allowing you to deal an additional 1d8 poison damage on each weapon attack. If the Creature is Poisoned you deal an additional 2d8 poison damage instead .

Experimental Toxins

 At 13th level, once per long rest, you can prepare a special set of Toxic cloud bottles that contain more diverse poisons. when you do so you can pick one of the following options: 

• Creatures Poisoned by your toxic clouds are now also Blinded for the same duration.
• Creatures Poisoned by your toxic clouds are now also Deafened for the same duration.
• Creatures Poisoned by your toxic clouds cannot use their reaction and have their movement speed halved.
• Your toxic clouds invigorate you. For one turn, your movement speed is doubled and you gain an additional action when you start your turn in a toxic cloud. That action can be used only to take the Attack (one weapon attack only), Dash, Disengage, Hide, or Use an Object action.

In addition your toxic clouds deals 2d8 damage every time a creature fails the Constitution save or none if they succeed.

Advanced Toxicology

Starting at 17th level, you gain immunity to Poison damage and can no longer be Poisoned.

Your toxins are also no longer affected by any resistances or immunities excluding your own.