Base Class: Rogue
Some rogues dabble in experiments with magical components which can often lead to explosive insights. Such rogues often prefer mixing up new poisons, potions, and explosives to prepare for any situation before things go awry. These rogues are often seen as tacticians, madmen, or untraceable killers, but many adventuring parties enjoy having a well-prepared member on their side.
When you choose this archetype at 3rd level, you gain proficiency with the poisoner's kit and alchemical supplies.
When you reach 3rd Level, you gain the ability to cast spells in the form of elixirs stored in various vials. These elixirs act differently than spells in that they are prepared at the beginning of the day or mixed as needed. To mix an elixir takes ten minutes to perform, or an hour to prepare up to all of your vials. Due to the focus required for properly mixing an elixir, they can only be prepared during a short or long rest. Mixing an elixir that for a spell that requires a cast time of more than a minute takes twice as long as normally casting the spell. The cost of preparing elixirs is also twice the cost of the material components for the associated spell. Once prepared, elixirs are usable once within 24 hours of their creation, after which they decompose to a useless sludge.
To use an elixir, their magic can be released in a number of ways. The magic is contained as a fluid within various vials, and as such when the vial is opened in some way then the magic is released with the spell's target being the creature touching the freed fluid. Potions with an area of effect have the vial as their point of origin, and fill an area according to how you have aimed the potion (or a random direction in the case of uncontrolled release, for example when a vial is smashed open). A vial can be thrown, as a ranged weapon attack, to a range of 20 feet, or 60 feet with disadvantage. Potions that contain concentration spells automatically last up to half of their maximum concentration time without needing to be maintained.
Spell Slots. The Alchemist Spellcasting table (identical to the Arcane Trickster Spellcasting table without cantrips) shows how many spell slots you have to create elixirs of 1st level and higher. Creating elixirs consumes the energy required to cast the spell normally, and as such you can only prepare a number of elixirs equal to the number of alchemist spell slots that you have. These spell slots can only be used for creating elixirs and you regain them when you finish a long rest. For example, if you wish to create an elixir of burning hands and have a 1st-level and a 2nd-level slot available, you can create the elixir using either slot and it's effects will change appropriately.
Spells Known of 1st-Level and Higher. You know three 1st-level wizard spells of your choice, which you must choose from the enchantment, evocation, illusion, necromancy, and transmutation spells on the wizard spell list. The Spells Known column of the Alchemist Spellcasting table shows when you learn more wizard spells of 1st level or higher. Each of these spells must be an enchantment, evocation, illusion, necromancy, or transmutation spell of your choice, and must be of a level for which you have spell slots. For instance, when you reach 7th level in this class, you may learn one new spell of 1st or 2nd level. Whenever you gain a level in this class, you can replace one of your choice with another spell of your choice from the wizard spell list, and it must be an enchantment, evocation, illusion, necromancy, or transmutation spell.
Spellcasting Ability. Intelligence is your spellcasting ability for your wizard spells, since you learn your spells through dedicated study, memorization, and calculation. You use your Intelligence whenever a spell refers to your spellcasting ability. In addition, you use your Intelligence modifier when setting the saving throw DC for a wizard spell you infuse into an elixir and when making an attack roll with an opened elixir. However, when you throw a vial you use your Dexterity modifier to make the attack roll.
Spell Save DC = 8 + your proficiency bonus + your intelligence modifier
Spell Attack Modifier = your proficiency bonus + your Intelligence modifier
By 9th level, you have come upon a formula for a dangerous mixture and mastered using it in combat. Choose one type of mixture from the selection below. You may apply this mixture to your weapon as a bonus action and it lasts for a minute before disappearing. You can only apply one dose of the mixture at any time. You can carry three vials of this mixture safely at a time, and you replenish your store of this mixture when you finish a long rest. Also, during the process of creating this mixture you've built up a resistance to it, gaining resistance to the damage type listed by the selected mixture, as well as a cure to the ailments of the mixture which can only be prepared and administered properly by you. You always carry some of the cure mixture on you and you can administer the cure as an action.
You have discovered a chemically active compound that eats away at your enemies. Applying this to your weapon adds an extra 1d6 acid damage when you hit a creature with that weapon. The creature must also make a Dexterity saving throw against your spell save DC or this damage persists, dealing an extra 1d6 acid damage to that creature at the beginning of each of its turns in combat for a number of rounds equal to your Intelligence modifier. As you level up in this class, you discover ways to make your acid more corrosive, dealing an extra 1d6 damage when you reach 13th level (2d6) and 17th level (3d6). These additional damage dice are also added to the persistent damage. When you choose this mixture, you gain resistance to acid damage.
You have discovered a magical fluid which burns away the very souls of your enemies. Applying this to your weapon adds an extra 1d8 necrotic damage when you hit a creature with that weapon. The creature must also make a Wisdom saving throw against your spell save DC or gain a level of exhaustion for a number of rounds equal to your Intelligence modifier. Successive uses of this poison on the same creature stack to a maximum of level 3 exhaustion (see PHB, Appendix A, pg. 291). As you level up in this class, you discover ways to make this fluid stronger, dealing an extra 1d8 necrotic damage at 13th (2d8) and 17th (level). When you choose this mixture, you gain resistance to necrotic damage.
You have discovered a new form of poison, unique to you. Applying this to your weapon adds an extra 1d10 poison damage when you hit a creature with that weapon. The creature must also make a Constitution saving throw against your spell save DC or become poisoned for a minute. As you level up in this class you discover ways to make your poison more potent, dealing an extra 1d10 damage when you reach 13th level (2d10) and 17th level (3d10). When you choose this mixture, you gain resistance to poison damage.
At 13th level, countless hours of practice have made you adept at mixing elixirs. Preparing elixirs now takes you half as long as they would normally take you, allowing you to create up to a maximum of 4 elixirs during a short rest. Also, you have mastered avoiding waste when you create your elixirs, cutting down on your costs and reducing the cost of producing potions by half.
At 17th level, a combination of exposure to strange chemicals and studying the nature of spells has given you knowledge beyond mortal understanding. Your Intelligence score is increased by 4 and your maximum for this score is 24.