Trapsmith

Trapsmiths are expert dungeoneers and mechanically inclined scouts, able to recognize and disarm traps and to set them for their enemies. These rogues prefer to scout ahead and use the terrain to their advantage—a trapsmith might be a monster hunter, guerilla warrior, tinkerer, or dungeon robber.

Bonus Expertise

When you choose this archetype at 3rd level, you gain proficiency with Engineering and tinker’s tools, and you gain an expertise die on checks made with either, and when using thieves’ tools. For you, expertise dice in these skills and tools can be upgraded from d8 to d10, exceeding the usual limit on expertise dice.

Cunning Trap

Starting at 3rd level, you can use your Cunning Action to spread caltrops or ball bearings, or to throw a vial containing holy water, acid, or the like. Vials are simple weapons for you and have the thrown property (20/40 feet). 

Trapmaking

Beginning at 3rd level, with 10 minutes of work you can use your thieves’ tools to boobytrap a 5-foot-square area or a Large or smaller object. Your trap can be anything from a needle in a lock to a rockfall in a passageway. Describe the mechanics of your trap to the Narrator. Logic determines which traps can be built where; for instance, a swinging axe can't be hidden in a jewelry box.

The trap's DC is 8 + your Dexterity bonus + your proficiency bonus. A creature can spot the trap by making a Perception check against the trap's DC. Creatures aware of the trap may avoid or disable it without a check. When a creature enters the trapped area or interacts with the trapped object it must succeed on a Dexterity saving throw against the trap's DC. On a failure, the trap is triggered and the creature takes an amount of damage equal to 1d6 damage times half your rogue level. The type of damage dealt (bludgeoning, piercing, slashing, or poison) is determined by the nature of your trap. Once a trap has been triggered, it is disabled.

You can use this feature a number of times equal to your proficiency bonus. You regain all uses of this feature when you finish a short or long rest .

Trap Sense

Also at 3rd level, you have advantage on saving throws made against traps. Ability checks made to detect and disarm traps are made with advantage and can be made using your Cunning Action.

Augmented Trapmaking

At 9th level, you invent a new way to increase the danger posed by your traps. You learn one of the following trap capabilities. When using Trapmaking to create a trap, you can choose to augment it with the new capability, which is triggered when your trap damages a creature.

Immobilization Trap

The target is caught in the jaws of a trap. The target’s movement speed is reduced to 0. A creature can use an action or legendary action to make a DC 13 Strength check, freeing itself or another creature on a success. Building this trap requires a hunting trap, which can be recovered after the trap is triggered.

Poison Trap

You may add a contact or injury poison to the trap (see Chapter 12: Gamemastery), which is consumed. The victim of the trap is affected by the poison. 

Vial Trap

Each creature within 5 feet of the trap must make a Dexterity saving throw or be splashed with a liquid, such as acid or alchemists' fire (see Chapter 4: Equipment). The liquid is consumed. 

Improvised Crafting

Starting at 13th level, you can use your tinker’s tools to create a mundane item during a short or long rest. You can create one of the following items, which lasts until the beginning of the next long or short rest . 

• A vial of alchemist’s fire or acid.
• Any weapon, ammunition, or gear from Chapter 4: Equipment which costs 20 gold or less (or several identical items with a total cost not exceeding 20 gold). The item functions like the original object but may be made of different materials. 

Deadly Trapmaking

Starting at 17th level, the traps you create with your Trapmaking feature deal an amount of damage equal to 1d6 damage times your rogue level