Thieves & Kings
Traps can be found almost anywhere. One wrong step in an ancient tomb might trigger a series of scything blades, which cleave through armor and bone. The seemingly innocuous vines that hang over a cave entrance might grasp and choke anyone who pushes through them. A net hidden among the trees might drop on travelers who pass underneath. In a fantasy game, unwary adventurers can fall to their deaths, be burned alive, or fall under a fusillade of Poisoned darts.
Most traps are triggered when a creature goes somewhere or touches something that the trap’s creator wanted to protect. Common triggers include stepping on a pressure plate or a false section of floor, pulling a trip wire, turning a door handle, and using the wrong key in a lock. Magic traps are often set to go off when a creature enters an area or touches an object. Some magic traps (such as the Glyph of Warding spell) have more complicated trigger conditions, including a password that prevents the trap from activating.
Usually some element of a trap is visible to careful inspection. Characters might notice an uneven flagstone that conceals a pressure plate, spot the gleam of light from a trigger, notice small, regular holes in the walls from which fire might erupt, or otherwise detect something that might reveal a trap’s presence.
A character actively looking for traps can attempt a Wisdom (Perception) check against the trap’s DC. A character’s Wisdom (Passive Perception) score will determine whether anyone notices the oddity surrounding the trap in passing. If detected before triggering it, they can attempt to disarm it, or avoid it, as they decide.
In most cases, you need to describe where you are looking in order for the DM to assign a chance for success. For example, a trap is a scything blade hidden inside the lid of a chest, that triggers upon opening. If you tell the DM that you pace around the room, looking at the walls and furniture for clues, you will have no chance of finding the trap, regardless of your Wisdom (Perception) check result. You must specify that you are examining the lock and the lid, and determining if opening it will trigger a trap, to get any chance of success.
Similarly, some traps become obvious once certain situations have been met. A trap door hidden under a large rug becomes obvious if the rug is removed, for example, and so no check is required under such a circumstance.
Any search for traps on a specific location is assumed to take roughly ten minutes.
Whenever you are attempting to remove a trap, you must first have identified such an item exists, as determined by your Wisdom (Perception) check above. Removal of traps is then an ability-based check, though some are mechanical and some are magical. Each requires its own method of handling. In both cases, Thieves’ Tools are essential. Proficiency with these tools allows a thief to add their Proficiency bonus (if any) to any ability checks made to disarm traps or open locks.
Disarming a Mechanical Trap : Mechanical traps include pits, arrow traps, falling blocks, water-filled rooms, scything blades and any other device requiring a mechanism to operate.
An Intelligence (Investigation) check is required to figure out what to do, and then a Dexterity (Thieves’ Tools) check is required to disarm it. Failure to discern the type of trap, or identify the source of the potential danger with the Intelligence (Investigation) check will stop the ability to disarm, as one cannot figure the trap out. Failure to disarm the trap with the Dexterity (Thieves’ Tools) check, will result in the trap’s activation, and whatever result that might entail.
Disarming a Magical Trap : Magical traps are either magical device traps or spell traps. Magical Device traps initiate spell effects when activated. Spell Traps are magical spells, such as “Glyph of Warding”, or “Symbol” that function as traps.
Any character, regardless of training, can attempt an Intelligence (Arcana) check to both detect and disarm a magical trap, in addition to whatever special notes might be attached to the specific spell or spell effect listed in the trap’s description. The DC for both checks is the same. In addition, Dispel Magic has a chance of disabling most magical traps, with the trap’s description often giving the DC required to do so.
In most cases, a trap’s description is sufficient to adjudicate whether or not a player’s actions are sufficient to locate or foil the trap. Clever play and planning will always override a die rolling attempt. Common sense will often determine the result of any actions.
Foiling traps can prove difficult. Consider a trapped chest. If the chest is opened without first pulling on the two handles located on the sides of the chest, a mechanism fires a hail of poisoned needles towards anyone in front of the chest as it is opened. After inspecting the chest, and determining after a couple failed rolls whether or not the chest is trapped, they take the precaution of placing a shield in front of the chest, and open it from the side using an iron rod. In this case, the trap triggers, but the hail of needles thud harmlessly into the shield.
Traps are often designed with mechanisms that allow them to be disarmed and otherwise bypassed. Intelligent monsters that place such devices around their lairs, require a means to pas these traps without harming themselves. Such traps have hidden levers that disable their triggers, or a secret door might conceal a passage to bypass around the trap.
The effects of traps can range from inconvenient to deadly, making use of such elements as arrows, spikes, blades, poison, toxic gas, blasts of alchemist’s fire, and deep pits. The deadliest traps combine multiple elements to kill, injure, contain, or drive off any creature unfortunate enough to trigger them.
Complex traps work like standard traps, except once activated, they execute a series of actions each round. A complex trap turns the process of dealing with a trap into something more like a combat encounter. These traps tend to have their own initiative, and on its turn, activate over and over again, making successive attacks against intruders, create effects that change over time, or otherwise produce a dynamic challenge. Otherwise, the complex trap can be detected and disabled or bypassed in the usual ways.
For example, a trap that causes a a room to slowly flood works best as a complex trap. On the trap’s turn, the water rises. After several rounds the room is completely flooded.