Trapmaster

You focus on dealing with one of the most unseen methods of attack; traps. Through deliberate planning, physical deftness, and a small amount of magic, trapmasters fill the battlefield with custom instruments of destruction and impairment. Rogues who embrace this archetype thrive on cramped corners and narrow passages, be they the alleys of a city or the crumbling cliff-sides of a canyon, and live to see the dominoes they've carefully laid collapse on their enemies.

The magic inside of the traps of these rogues often informs their origin. Those from Al'Taj often rely on pottery with elementally infused dust, while those in Keeper's Coast craft metal housings filled with blast powder. Regardless of shape or origin, the devices of a trapmaster are uniquely volatile, and never harmless.

Sapper's Hands

3rd-level Trapmaster feature

Your skill with sabotage transcends your magical traps. You gain proficiency with tinker's tools, and the DC of non-magical adventuring gear you place (such as ball bearings) is equal to 10 + half your rogue level (rounded down), unless it would be higher. Finally, you have advantage on ability checks and saving throws made to disarm or resist the effects of traps.

Eldritch Device

3rd-level Trapmaster feature

You've learned how to make special traps known as eldritch devices. As part of a long rest, you can craft a number of these traps equal to your Intelligence modifier (minimum of 1), which last until the end of your next long rest. You can also craft one eldritch device as part of a short rest, and you can never have more eldritch devices than your Intelligence modifier (minimum of 1). Damage dealt by an eldritch device counts as magical for the purpose of overcoming resistance and immunity to nonmagical damage.

Saving Throws. Your eldritch devices require your target(s) to make a saving throw to resist the device's effects. The saving throw DC is calculated as follows:

Eldritch Device save DC = 8 + your proficiency bonus + your Intelligence modifier

As a bonus action you can place one of your eldritch devices in an unoccupied space within 5 feet that has no other traps. If conditions allow, you can make a Dexterity (Sleight of Hand) check to conceal the eldritch device among the terrain as part of the same bonus action. The eldritch device is then hidden unless a creature succeeds on a Wisdom (Perception) check against the total of the check you made when you placed it. You always know where your traps are, and can use your action to pick them back up.

An eldritch device detonates when a creature enters its space or when you use an action to manually detonate one within 30 feet of you. An eldritch device affects all creatures within 5 feet of it when it detonates, and the effects are based on the device's type, which you decide when you place it:

• Shrapnel. Affected creatures must succeed on a Dexterity saving throw or take piercing damage equal to a roll of your Sneak Attack dice and have their speed reduced by 10 feet until the end of your next turn, taking half as much damage and no speed reduction on a success.
• Smoke. Affected creatures must succeed on a Constitution saving throw or subtract a d4 from any attack rolls and saving throws they make before the end of your next turn. The area is then heavily obscured until the end of your next turn.
• Snare. Affected creatures must succeed on a Strength saving throw or be restrained until the end of your next turn, taking slashing damage equal to half of a roll of your Sneak Attack dice (rounded up) on a success. A creature can use its action to make a Strength check against your Eldritch Device save DC, freeing itself or another creature within its reach on a success.

Subtle Creations

9th-level Trapmaster feature

You've learned how to refine your traps and make new ones for espionage purposes. The range you can place and manually detonate your traps is doubled, and you ignore traits that grant advantage against magical effects. In addition, your traps can deal acid, cold, fire, lightning, or thunder damage instead of their normal type.

Finally, you gain two new Eldritch Device options:

• Seek. Affected creatures must succeed on a Wisdom saving throw or have an invisible marker placed on them for a number of hours equal to your proficiency bonus. While they have this marker, your attacks against them deal an extra 1d6 psychic damage, and you have advantage on ability checks to track or locate them.
• Spy. The trap becomes invisible, and allows you to see and hear what it can for the next 10 minutes. It has darkvision and can only perceive things within 30 feet of itself. It also counts as an object with 5 HP and 18 AC. Other creatures can't notice this trap unless they have blindsight, truesight, or some other way of seeing through magical invisibility.

Improved Traps

13th-level Trapmaster feature

You've found new ways to augment your traps even further. The area affected by your eldritch devices increases to 10 feet. Additionally, you can set conditions for your traps to activate when you place them, such as when an enemy attacks or when a creature says a specific phrase. When that condition is met within 10 feet of the eldritch device, you can use your reaction to manually detonate it.

Heart of Sabotage

17th-level Trapmaster feature

You've invented the perfect device for sundering foes and terrain alike. As an action, you can attach a special adhesive trap to a creature or object within 5 feet. At the start of your next turn, the target takes 12d8 force damage (doubled for objects) and suffers a -2 penalty to their AC for one minute, as the damage from the trap sunders their body. A creature can use their action to make a DC 20 Athletics check to remove it, dropping it harmlessly in an unoccupied space on a success. 

Once you use this special trap, you cannot use it again until you finish a long rest, unless you expend one of your Eldritch Devices to make a new one.