Saboteur

Disrupting enemy supply routs, setting a fiery ambush or bringing down buildings, saboteurs are silent and precise until the right moment, when they become anything but those two things. Crafting dangerous alchemical formulas and traps, saboteurs are experts of controlled destruction.

Tools of the trade

When you choose this archetype at 3rd level, you gain proficiency with alchemists supplies and improvised weapons. Improvised weapons count as finesse weapons for you. 

In addition, when you complete a long rest and have alchemists tools in hand, you can create a number of items equal to your proficiency modifier + your intelligence modifier. These items may be an acid (vial), alchemist's Fire (flask), hunting trap or ball Bearings (bag of 1,000).

The makeshift nature of these devises makes them break down or loose their alchemical potency at the start of your next long rest. 

As you gain levels in this class you may attempt to invent and craft your own unique devices at your DMs discretion.

Death from below

While hidden, you can spend an action to set one of your devices as a trap. A creature that is actively searching for your trap can make a perception check against your passive stealth (10 plus your bonus to the stealth skill) in order to spot it, otherwise they use their passive perception against your passive stealth. You may trigger your trap as an action, or as a reaction when a creature enters its area of effect, as long as you are no more than 30 feet away from the trap. If a creature is not aware of the trap, the trap also deals your sneak attack damage(sneak attack can only happen once per turn). The trap can only deal sneak attack damage to a single creature. A creature that finds one of your traps may attempt to disarm it as an action if they have thieves tools and are proficient with them. The DC to disarm one of your traps is 8 + your proficiency modifier + your intelligence modifier.

Advanced pyrotechnics

At ninth level you perfect the manufacturing process for your devices, making them more reliably deadly. 

If any of your devices require a saving throw, your proficiency and intelligence modifiers are added to the base save DC of the item.

In addition, you can use your cunning action to attack with one of your devices.

Finally, you perfect the designs of your tools to be devastating towards non living material. Creatures and objects made of inorganic material such as stone, crystal, or metal have disadvantage on saving throws against your devices.

Volatile compound

You can apply a volatile alchemical compound to one of your traps order devices, changing the area of effect to a 15 foot radius sphere. You must declare use of this ability before attacking with a device or setting it up as a trap. If your sneak attack triggers for that device, you deal half of your sneak attack dice (rounded down) to all creatures in the devices area of effect instead of all dice to a single creature.
Once you use this feature you can not use it again until you complete a long rest. 

In addition, your intelligence modifier is added to the total damage of your devices. This bonus applies to both traps and device attacks. 

Master of disaster

The base number of damage dice for all of your devices becomes 4. The type of dice and the damage type do not change (for example, your flask of alchemists fire now deals 4d4 fire damage instead of 1d4).

In addition, whenever you fail to disarm any trap, you may roll a Dexterity save with a DC of 15. On a successful save, the trap does not trigger.

Finally, you may use volatile compound twice instead of once per long rest.