Traps

From Dungeon Master's Guide, pages 105-106, 110-11, and 120-121; and Xanathar's Guide to Everything, pages 113-119.

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 the D&D game, unwary adventurers can fall to their deaths, be burned alive, or fall under a fusillade of poisoned darts.

A trap can be either mechanical or magical in nature. Mechanical traps include pits, arrow traps, falling blocks, water-filled rooms, whirling blades, and anything else that depends on a mechanism to operate. Magic traps are either magical device traps or spell traps. Magical device traps initiate spell effects when activated. Spell traps are spells such as glyph of warding and symbol that function as traps.

Traps in Play
When adventurers come across a trap, you need to know how the trap is triggered and what it does, as well as the possibility for the characters to detect the trap and to disable or avoid it.

Triggering a Trap
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 doorknob, 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.

Detecting and Disabling a Trap
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 off a trip wire, notice small holes in the walls from which jets of flame will erupt, or otherwise detect something that points to a trap's presence.

A trap's description specifies the checks and DCs needed to detect it, disable it, or both. A character actively looking for a trap can attempt a Wisdom (Perception) check against the trap's DC. You can also compare the DC to detect the trap with each character's passive Wisdom (Perception) score to determine whether anyone in the party notices the trap in passing. If the adventurers detect a trap before triggering it, they might be able to disarm it, either permanently or long enough to move past it. You might call for an Intelligence (Investigation) check for a character to deduce what needs to be done, followed by a Dexterity check using thieves' tools to perform the necessary sabotage.

Any character can attempt an Intelligence (Arcana) check to detect or disarm a magic trap, in addition to any other checks noted in the trap's description. The DCs are the same regardless of the check used. In addition, dispel magic has a chance of disabling most magic traps. A magic trap's description provides the DC for the ability check made when you use dispel magic.

In most cases, a trap's description is clear enough that you can adjudicate whether a character's actions locate or foil the trap. As with many situations, you shouldn't allow die rolling to override clever play and good planning. Use your common sense, drawing on the trap's description to determine what happens. No trap's design can anticipate every possible action that the characters might attempt.

You should allow a character to discover a trap without making an ability check if an action would clearly reveal the trap's presence. For example, if a character lifts a rug that conceals a pressure plate, the character has found the trigger and no check is required.

Foiling traps can be a little more complicated. Consider a trapped treasure chest. If the chest is opened without first pulling on the two handles set in its sides, a mechanism inside fires a hail of poison needles toward anyone in front of it. After inspecting the chest and making a few checks, the characters are still unsure if it's trapped. Rather than simply open the chest, they prop a shield in front of it and push the chest open at a distance with an iron rod. In this case, the trap still triggers, but the hail of needles fires harmlessly into the shield.

Traps are often designed with mechanisms that allow them to be disarmed or bypassed. Intelligent monsters that place traps in or around their lairs need ways to get past those traps without harming themselves. Such traps might have hidden levers that disable their triggers, or a secret door might conceal a passage that goes around the trap.

Trap Effects
The effects of traps can range from inconvenient to deadly, making use of elements such as arrows, spikes, blades, poison, toxic gas, blasts of fire, and deep pits. The deadliest traps combine multiple elements to kill, injure, contain, or drive off any creature unfortunate enough to trigger them. A trap's description specifies what happens when it is triggered.

The attack bonus of a trap, the save DC to resist its effects, and the damage it deals can vary depending on the trap's severity. Use the Trap Save DCs and Attack Bonuses table and the Damage Severity by Level table for suggestions based on three levels of trap severity.

A trap intended to be a setback is unlikely to kill or seriously harm characters of the indicated levels, whereas a dangerous trap is likely to seriously injure (and potentially kill) characters of the indicated levels. A deadly trap is likely to kill characters of the indicated levels.

Complex Traps
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.

When a complex trap activates, it rolls initiative. The trap's description includes an initiative bonus. On its turn, the trap activates again, often taking an action. It might make successive attacks against intruders, create an effect that changes 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 room to slowly flood works best as a complex trap. On the trap's turn, the water level rises. After several rounds, the room is completely flooded.

Traps Revisited
The rules for traps in the dungeon master's guide provide the basic information you need to manage traps at the game table. The material here takes a different, more elaborate approach-describing traps in terms of their game mechanics and offering guidance on creating traps of your own using these new rules.

Rather than characterize traps as mechanical or magical, these rules separate traps into two other categories: simple and complex.

Making Traps Meaningful
If you want to improve the chance that the characters will come up against the traps you've set for them in an encounter or an adventure, it can be tempting to use a large number of traps. Doing so ensures that the characters will have to deal with at least one or two of them, but it's better to fight that urge.

If your encounters or adventures are sown with too many traps, and if the characters are victimized over and over again as a result, they are likely to take steps to prevent further bad things from happening. Because of their recent experience, the characters can become overly cautious, and you run the risk of the action grinding to a halt as the players search every square inch of the dungeon for trip wires and pressure plates.

Traps are most effective when their presence comes as a surprise, not when they appear so often that the characters spend all their effort watching out for the next one.

Simple Traps
A simple trap activates and is thereafter harmless or easily avoided. A hidden pit dug at the entrance of a goblin lair, a poison needle that pops from a lock, and a crossbow rigged to fire when an intruder steps on a pressure plate are all simple traps.

Elements of a Simple Trap
The description of a simple trap begins with a line that gives the trap's level and the severity of the threat it poses. Following a general note on what the trap looks like and how it functions are three paragraphs that tell how the trap works in the game.


 * Level and Threat: A trap's level is actually a range of levels, equivalent to one of the tiers of play (levels 1-4, 5-10, 11-16, and 17-20), indicating the appropriate time to use the trap in your campaign. Additionally, each trap poses either a moderate, dangerous, or deadly threat, based on its particular details.
 * Trigger: A simple trap activates when an event occurs that triggers it. This entry in a trap's description gives the location of the trigger and the activity that causes the trap to activate.
 * Effect: A trap's effect occurs after it activates. The trap might fire a dart, unleash a cloud of poison gas, cause a hidden enclosure to open, and so on. This entry specifies what the trap targets, its attack bonus or saving throw DC, and what happens on a hit or a failed saving throw.
 * Countermeasures: Traps can be detected or defeated in a variety of ways by using ability checks or magic. This entry in a trap's description gives the means for counteracting the trap. It also specifies what happens, if anything, on a failed attempt to disable it.

Running a Simple Trap
To prepare for using a simple trap in play, start by making note of the characters' passive Wisdom (Perception) scores. Most traps allow Wisdom (Perception) checks to detect their triggers or other elements that can tip off their presence. If you stop to ask players for this information, they might suspect a hidden danger.

When a trap is triggered, apply its effects as specified in its description.

If the characters discover a trap, be open to adjudicating their ideas for defeating it. The trap's description is a starting point for countermeasures, rather than a complete definition.

To make it easier for you to describe what happens next, the players should be specific about how they want to defeat the trap. Simply stating the desire to make a check isn't helpful for you. Ask the players where their characters are positioned and what they intend to do to defeat the trap.

Designing Simple Traps
You can create your own simple traps by using the following guidelines. You can also adapt the example traps for different levels and severity of threat by modifying their DCs and damage values as shown below.

Purpose
Before diving into the details of your trap, think about its reason for being. Why would someone build such a trap? What is its purpose? Consider the trap's creator (in the adventure), the creator's purpose, and the location the trap protects. Traps have context in the world-they aren't created for no reason-and that context drives the trap's nature and effects.

Described below are a few of the general purposes a trap might have. Use them to inspire the creation of your own traps.


 * Alarm: An alarm trap is designed to alert an area's occupants of intruders. It might cause a bell or a gong to sound. This type of trap rarely involves a saving throw, because the alarm can't be avoided when the trap goes off.
 * Delay: Some traps are designed to slow down enemies, giving a dungeon's inhabitants time to mount a defense or flee. The hidden pit is a classic example of this kind of trap. A 10-foot-deep pit usually deals little damage and is easy to escape, but it serves its purpose by impeding intruders. Other examples of delaying traps include collapsing walls, a portcullis that drops from the ceiling, and a locking mechanism that shuts and bars a door.
 * If a delaying trap has moving parts that directly threaten characters when they operate, the characters are usually required to make Dexterity saving throws to avoid harm.


 * Restrain: A restraining trap tries to keep its victims in place, leaving them unable to move. Such traps are often employed in conjunction with regular guard patrols, so that victims are periodically extricated and taken away to be dealt with. But in an ancient dungeon, the guards might be long gone.
 * Restraining traps usually require a successful Strength saving throw to be avoided, but some don't allow saving throws. In addition to dealing damage, a restraining trap also renders a creature unable to move. Making a subsequent successful Strength check (using the trap's saving throw DC) or dealing damage against the trap can break it and free the captive. Examples include a bear trap, a cage that drops from a ceiling, and a device that flings a net.


 * Slay: Some traps are designed to eliminate intruders, plain and simple. Their effects include poisoned needles that spring out when a lock is tampered with, blasts of fire that fill a room, poison gas, and other lethal measures. Saving throws-usually Dexterity or Constitution-allow creatures to avoid or mitigate the trap's effects.

Level and Lethality
Before creating a trap's effects, think about its level and its lethality.

Traps are divided into four level ranges: 1-4, 5-10, 11-16, and 17-20. The level you choose for a trap gives you a starting point for determining its potency.

To further delineate the trap's strength, decide whether it is a moderate, dangerous, or deadly threat to characters in its level range. A moderate trap is unlikely to kill a character. A dangerous trap typically deals enough damage that a character hit by one is eager for healing. A deadly trap might reduce a creature to 0 hit points in one shot, and leaves most creatures hit by it in need of a short or long rest.

Consult the following tables when determining a trap's effects. The Trap Save DCs and Attack Bonuses table provides guidelines for a trap's saving throw DC, check DC, and attack bonus. The check DC is the default for any check used to interact with the trap.

The Damage Severity by Level table lists the typical damage a trap deals at certain character levels. The damage values given assume that the trap damages one creature. Use d6s for damage in place of d10s for traps that can affect more than one creature at a time.

The Spell Equivalent by Level table shows the spell slot level that is appropriate for a given character level and the severity of danger posed by the trap. A spell is a great foundation to use as the design of a trap, whether the trap duplicates the spell (a mirror that casts charm person on whoever looks into it) or uses its effects (an alchemical device that explodes like a fireball).

The Deadly entry for characters of 17th level or higher suggests combining a 9th-level and a 5th-level spell into one effect. In this case, pick two spells, or combine the effects of a spell cast using a 9th-level and a 5th-level slot. For instance, a fireball spell of this sort would deal 24d6 fire damage on a failed saving throw.

Triggers
A trigger is the circumstance that needs to take place to activate the trap.

Decide what causes the trap to activate and determine how the characters can find the trigger. Here are some example triggers:
 * A pressure plate that, when it is stepped on, activates the trap
 * A trip wire that springs a trap when it is broken, usually when someone walks through it
 * A doorknob that activates a trap when it is turned the wrong way
 * A door or chest that triggers a trap when it is opened

A trigger usually needs to be hidden to be effective. Otherwise, avoiding the trap is usually easy.

A trigger requires a Wisdom (Perception) check if simply spotting it reveals its nature. The characters can foil a pit trap hidden by a leaf-covered net if they spot the pit through a gap in the leaves. A trip wire is foiled if it is spotted, as is a pressure plate.

Other traps require careful inspection and deduction to notice. A doorknob opens a door when turned to the left, but activates a trap when turned to the right. Such a subtle trap requires a successful Intelligence (Investigation) check to notice. The trigger is obvious. Understanding its nature is not.

The DC of the check, regardless of its type, depends on the skill and care taken to conceal the trap. Most traps can be detected with a successful DC 20 check, but a crudely made or hastily built trap has a DC of 15. Exceptionally devious traps might have a DC of 25.

You must then put some thought into what the characters learn with a successful check. In most cases, the check reveals the trap. In other cases, it uncovers clues, but foiling the trap still requires some deduction. The characters might succeed on the check but still trigger the trap if they don't understand what they have learned.

Effects
Designing a trap's effects is a straightforward process. The tables for saving throw DCs, attack bonuses, damage, and the like give you a starting point for most simple traps that deal damage.

For traps with more complex effects, your best starting point is to use the Spell Equivalent by Level table to find the best match for your trap's intended effect. Spells are a good starting point because they are compact pieces of game design that deliver specific effects.

If you are using a spell as a starting point, check to see if you need to tweak its effects to fit the trap's nature. For instance, you can easily change the damage type a spell delivers or the saving throw it requires.

Disarming a Simple Trap
Only one successful ability check is required to disarm a simple trap. Imagine how your trap operates, and then think about how the characters could overcome it. More than one kind of ability check might be possible. Some traps are so poorly concealed that they can be discovered or circumvented without active effort. For instance, a hidden pit trap is effectively disarmed as soon as the characters notice it. After that, they can simply walk around it, or they can climb down one side, walk across the bottom of the pit, and climb up the other side.

Once you determine how a trap can be disarmed or avoided, decide the appropriate ability and skill combinations that characters can use. A Dexterity check using thieves' tools, a Strength (Athletics) check, and an Intelligence (Arcana) check are all commonly used for this purpose.

A Dexterity check using thieves' tools can apply to any trap that has a mechanical element. Thieves' tools can be used to disable a trip wire or a pressure plate, disassemble a poison needle mechanism, or clog a valve that leaks poisonous gas into a room.

A Strength check is often the method for thwarting traps that can be destroyed or prevented from operating through the use of brute force. A scything blade can be broken, a sliding block can be held in place, or a net can be torn apart.

A magic trap can be disabled by someone who can undermine the magic used to power it. Typically, a successful Intelligence (Arcana) check enables a character to figure out how a magic trap functions and how to negate its effect. For instance, the character could discover that a statue that belches a jet of magical flame can be disabled by shattering one of its glass eyes.

Once you know what kind of check is called for, you then determine what happens on a failed attempt to disable the trap. Depending on the kind of check involved and the nature of the trap, you might determine that any failed check has negative consequences-usually involving the triggering of the trap. At other times, you could assign a number that the check must exceed to prevent the trap from going off. If the total of the check is equal to or lower than that number, the trap activates.

Placing a Simple Trap
Context and environment are critical when it comes to properly locating a trap. A swinging log trap that's meant to knock characters aside is a mere inconvenience on a typical forest path, where it can be easily circumvented. But it's a potentially deadly hazard on a narrow trail that hugs the side of a towering cliff face.

Choke points and narrow passages that lead to important places in a dungeon are good spots for traps, especially those that serve as alarms or restraints. The goal is to foil or delay intruders before they can reach a critical location, giving the dungeon's denizens a chance to mount a defense or a counterattack.

A treasure chest, a door leading to a vault, or any other obstacle or container that bars the way to a valuable treasure is the ideal location for a slaying trap. In such instances, the trap is the last line of defense against a thief or intruder.

Alarm traps, since they pose no direct physical threat, are appropriate for areas that are also used by a dungeon's denizens-assuming the residents know about the trap and how to avoid setting it off. Accidents can happen, but if a goblin stumbles inside its den and activates an alarm trap, there's no real harm done. The alarm sounds, the guards arrive, they punish the clumsy goblin, and they reset the trap.

Complex Traps
A complex trap poses multiple dangers to adventurers. After a complex trap activates, it remains dangerous round after round until the characters avoid it or disable it. Some complex traps become more dangerous over time, as they accumulate power or gain speed.

Complex traps are also more difficult to disable than simple ones. A single check is not enough. Instead, a series of checks is required to slowly disengage the trap's components. The trap's effect degrades with each successful check until the characters finally deactivate it.

Most complex traps are designed so that they can be disarmed only by someone who is exposed to the trap's effect. For example, the mechanism that controls a hallway filled with scything blades is on the opposite end from the entrance, or a statue that bathes an area in necrotic energy can be disabled only by someone standing in the affected area.

Describing a Complex Trap
A complex trap has all the elements of a simple trap, plus special characteristics that make the trap a more dynamic threat. Level and Threat.

A complex trap uses the same level and severity designations that a simple trap does.


 * Trigger: Just like a simple trap, a complex trap has a trigger. Some complex traps have multiple triggers.
 * Initiative: A complex trap takes turns as a creature does, because it functions over a period of time. This part of a trap's description tells whether the trap is slow (acts on initiative count 10), fast (acts on initiative count 20), or very fast (acts on initiative count 20 and also initiative count 10). A trap always acts after creatures that have the same initiative count.
 * Active Elements: On a trap's turn, it produces specific effects that are detailed in this part of its description. The trap might have multiple active elements, a table you roll on to determine its effect at random, or options for you to choose from.
 * Dynamic Elements: A dynamic element is a threat that arises or evolves while the trap functions. Usually, changes involving dramatic elements take effect at the end of each of the trap's turns or in response to the characters' actions.
 * Constant Elements: A complex trap poses a threat even when it is not taking its turn. The constant elements describe how these parts of the trap function. Most make an attack or force a saving throw against any creature that ends its turn within a certain area.
 * Countermeasures: A trap can be defeated in a variety of ways. A trap's description details the checks or spells that can detect or disable it. It also specifies what happens, if anything, on a failed attempt to disable it.

Disabling a complex trap is like disarming a simple trap, except that a complex trap requires more checks. It typically takes three successful checks to disable one of a complex trap's elements. Many of these traps have multiple elements, requiring a lot of work to shut down every part of the trap. Usually, a successful check reduces a trap element's effectiveness even if it doesn't disable the trap.

Running a Complex Trap
A complex trap functions in play much like a legendary monster. When it is activated, the trap's active elements act according to its initiative. On each of its initiative counts, after all creatures with that same initiative count have acted, the trap's features activate. Apply the effects detailed in the trap's description.

After resolving the effects of the trap's active elements, check its dynamic elements to see if anything changes about the trap. Many complex traps have effects that vary during an encounter. A magical aura might do more damage the longer it is active, or a swinging blade might change which area of a chamber it attacks.

The trap's constant elements allow it to have effects when it isn't the trap's turn. At the end of each creature's turn, look at the trap's constant elements to see if any of their effects are triggered.

Experience for Complex Traps
Overcoming a complex trap merits an experience point award, depending on the danger it poses. Judging whether a party has overcome a trap requires some amount of adjudication. As a rule of thumb, if the characters disable a complex trap or are exposed to its effects and survive, award them experience points for the effort according to the table below.

Designing Complex Traps
Creating a complex trap takes more work than building a simple one, but with some practice, you can learn the process and make it move quickly.

Familiarize yourself with the advice on designing a simple trap before proceeding with the guidelines on complex traps.

Purpose
Complex traps are typically designed to protect an area by killing or disabling intruders. It is worth your time to consider who made the trap, the trap's purpose, and its desired result. Does the trap protect a treasure? Does it target only certain kinds of intruders?

Level and Lethality
Complex traps use the same level designations and lethality descriptors that simple traps do. Refer to that section for a discussion of how level and lethality help determine saving throw and check DCs, attack bonuses, and other numerical elements of a complex trap.

Map
A complex trap has multiple parts, typically relies on the characters' positions to resolve some of its effects, and can bring several effects to bear in each round. The traps are called complex for a reason! To begin the design process, consider drawing a map of the area to be affected by the trap on graph paper, using a scale of 5 feet per square. This level of detail allows you to develop a clear idea of what the trap can do and how each of its parts interact. Your map is the starting point and context for the rest of the design process.

Don't limit yourself to one room. Look at the passages and rooms around the area of the trap and think about the role they can play. The trap might cause doors to lock and barriers to fall into place to prevent escape. It could cause darts to fire from the walls in one area, forcing characters to enter rooms where other devices trigger and threaten them.

Consider how terrain and furniture can add to the trap's danger. A chasm or a pit might create a buffer that allows a trap to send bolts of magic at the characters, while making it difficult or even impossible for them to reach the runes they must deface to foil that attack.

Think of your map like a script. Where do the characters want to go? What does the trap protect? How can the characters get there? What are their likely escape routes? Answering these questions tells you where the trap's various elements should be placed.

Active Elements
A complex trap's active elements work the same way as a simple trap's effects, except that a complex trap activates in every round. Otherwise, the guidelines for picking saving throw DCs, attack bonuses, and damage are the same. To make your trap logically consistent, make sure the elements you design can activate each round. For instance, ordinary crossbows rigged to fire at the characters would need a mechanism for reloading them between attacks.

In terms of lethality, it's better to have multiple dangerous effects in a trap than a single deadly one. For example, the Path of Blades trap uses two dangerous elements and one moderate element.

It's useful to create multiple active elements, with each affecting a different area. It's also a good idea to use a variety of effects. Some parts of the trap might deal damage, and others might immobilize characters or isolate them from the rest of the party. A bashing lever might knock characters into an area engulfed by jets of flame. Think about how the elements can work together.

Constant Elements
In addition to the active steps a complex trap takes, it should also present a continual hazard. Often, the active and constant effects are the same thing. Imagine a hallway filled with whirling saw blades. On the trap's turn, the blades attack anyone in the hall. In addition, anyone who lingers in the hallway takes damage at the end of each of their turns, accounting for the constant threat that the blades pose.

A constant element should apply its effect to any creature that ends its turn in that element's area. If an active element presents a threat when it isn't the trap's turn, define the threat it poses as a constant element. As a rule of thumb, keep the saving throw DC or attack bonus the same as for the active element but reduce the damage by half.

Avoid filling the entire encounter area with constant elements. Part of the challenge of a complex trap lies in figuring out which areas are safe. A moment's respite can help add an element of pacing to an encounter with a complex trap and give the characters the feeling that they aren't in constant peril. For example, walls that slam together might need to reset between slams, making them harmless when it isn't their turn to act.

Dynamic Elements
Just as a battle is more interesting if the monsters change their tactics or unveil new abilities in later rounds, so too are complex traps more fun if their nature changes in some way. The whirling blades that protect a treasure chest do more damage each round as they speed up. The poison gas in a room grows thicker as more of it floods the chamber, dealing greater damage and affecting line of sight. The necrotic aura around an idol of Demogorgon produces random effects each time its active element is triggered. As water floods a chamber, the characters must swim across areas they could walk through just a round or two earlier.

Since a complex trap remains active over the course of several rounds, it might be possible to predict its future behavior by examining how it functions. This information can give its targets a much better chance of thwarting it. To minimize this possibility, design your trap so that it presents multiple threats that can change each round. The changes can include how a trap targets creatures (different attacks or saving throws), the damage or effects it produces, the areas it covers, and so on. Some traps might have a random effect each round, while others follow a carefully programmed sequence of attacks.

Dynamic elements usually occur according to a schedule.

For a room that floods, you can plan out how the rising water level affects the area each round. The water might be ankle deep at the end of the first round, knee deep the next, and so on. Not only does the water bring a risk of drowning, it also makes it harder to move across the area. On the other hand, the rising water level might allow characters to swim to the upper reaches of the chamber that they couldn't get to from the floor.

Dynamic elements can also come into play in reaction to the characters' actions. Disarming one element of the trap might make the others deadlier. Disabling a rune that triggers a fire-breathing statue might cause the statue to explode.

Triggers
The advice on triggers given for simple traps also applies to complex traps, with one exception. Complex traps have multiple triggers, or are designed such that avoiding a trigger prevents intruders from reaching the area the trap guards. Other complex traps use magical triggers that activate on specific cues, such as when a door opens or someone enters an area without wearing the correct badge, amulet, or robe.

Look at your map and consider when you want the trap to spring into action. It's best to have a complex trap trigger after the characters have committed to exploring an area. A simple trap might activate when the characters open a door. A complex trap that triggers so early leaves the characters still outside the trapped room, in a place where they could decide to close the door and move on. A simple trap aims to keep intruders out. A complex trap wants to lure them in, so that when it activates, the intruders must deal with the trap before they can escape.

The trigger for a complex trap should be as foolproof as you can make it. A complex trap represents a serious expenditure of effort and magical power. No one builds such a trap and makes it easy to avoid. Wisdom (Perception) and Intelligence (Investigation) checks might be unable to spot a trigger, especially a magical one, but they can still give hints about the trap before it triggers. Bloodstains, ashes, gouges in the floor, and other clues of that sort can serve as evidence of the trap's presence.

Initiative
A complex trap acts repeatedly, but unlike characters and monsters, traps don't roll for initiative. As mechanical or magical devices, their active elements operate in a periodic manner. When designing a complex trap, you need to decide when and how often its active elements produce their effects.

In a trap with multiple active elements that work in concert, those different elements would act on different initiative counts. For instance, on initiative count 20, blades sweep across a treasure vault, driving the characters back into the hallway. On initiative count 10, magic darts fire from statues in the hallway while a portcullis falls to confine the characters.


 * Initiative 10: If a trap's active element takes time to build up its effects, then it acts on initiative count 10. This option is good for a trap that functions alongside allied monsters or other guardians; the delay before it acts can give guards the chance to move out of its area or force characters into the area before the trap triggers.
 * Initiative 20: If an element is designed to surprise intruders and hit them before they can react, then it acts on initiative count 20. This option is generally best for a complex trap. Think of it as the default. Such a trap acts quickly enough to take advantage of most characters, with nimble characters like rogues, rangers, and monks having the best chance to move out of the area before the element activates.
 * Initiative 20 and 10: Some active elements are incredibly fast acting, laying waste to intruders in a few moments unless countered. They act on initiative count 20 and 10.

Defeating Complex Traps
A complex trap is never defeated with a single check. Instead, each successful check foils some part of it or degrades its performance. Each element of the trap must be overcome individually to defeat the trap as a whole.

As part of determining how your trap can be overcome, look at your map and consider where the characters must be located to attempt an action that can foil part of the trap. As a rule, the characters should need to be near or adjacent to an element to have a chance of affecting it. An element can be designed so that it protects itself. A fighter might be able to break a whirling blade, but moving close enough to attack it requires giving the blade a chance to strike.

What methods are effective against your trap? Obvious candidates are activities covered by the same sorts of checks used to defeat simple traps, but use your knowledge of the trap's design to identify other options. A valve that leaks poison gas into a room can be stopped up. A statue that emits a deadly aura can be pushed over and smashed. Attacks, spells, and special abilities can all play a role in undermining a trap.

Leave room for improvisation by the characters. Don't create a few predetermined solutions and wait for the players to figure out the right approach. If you understand the mechanism behind how a trap works, that makes it much easier for you to respond to the players' ideas. If a character wants to try something you haven't allowed for, pick an ability, assess the chance of success, and ask for a roll.

Shutting down one part of a complex trap usually requires multiple successes. As a default, it takes three successful checks or actions to disable an element. The first successful check might reduce the element's saving throw DC or attack bonus. The second successful check might halve the element's damage, and the final successful check shuts it down.

For elements that don't attack, allow each successful check to reduce that element's effectiveness by one-third. A lock's DC is decreased, or a gate opens wide enough to allow a Small character to squeeze through it. A mechanism pumping poison gas into the room becomes defective, causing the gas's damage to increase more slowly or not at all.

It takes time to disable a complex trap. Three characters can't make checks in rapid succession to disarm a complex trap in a matter of seconds. Each would get in another character's way and disrupt the effort. Once a character succeeds on a check, another character can't attempt the same check against the same trap element until the end of the successful character's next turn.

Not all of the characters' options need to be focused on stopping a trap from operating. Think of what characters can do to mitigate or avoid a trap's effects. Making the trap vulnerable to this sort of effort is a way to engage characters who might be ill-suited to confront the trap directly. A successful Intelligence (Religion) check might provide insight into the imagery displayed by a trap in a temple or shrine, giving other characters a clue about how and where to direct their efforts. A character could stand in front of a dart trap while holding a shield that the darts can target harmlessly, while other characters trigger that element as they work to disable it.

If a character wants to try something you haven't allowed for, pick an ability, assess the chance of success, and ask for a roll.

Shutting down one part of a complex trap usually requires multiple successes. As a default, it takes three successful checks or actions to disable an element. The first successful check might reduce the element's saving throw DC or attack bonus. The second successful check might halve the element's damage, and the final successful check shuts it down.

For elements that don't attack, allow each successful check to reduce that element's effectiveness by one-third. A lock's DC is decreased, or a gate opens wide enough to allow a Small character to squeeze through it. A mechanism pumping poison gas into the room becomes defective, causing the gas's damage to increase more slowly or not at all.

It takes time to disable a complex trap. Three characters can't make checks in rapid succession to disarm a complex trap in a matter of seconds. Each would get in another character's way and disrupt the effort. Once a character succeeds on a check, another character can't attempt the same check against the same trap element until the end of the successful character's next turn.

Not all of the characters' options need to be focused on stopping a trap from operating. Think of what characters can do to mitigate or avoid a trap's effects. Making the trap vulnerable to this sort of effort is a way to engage characters who might be ill-suited to confront the trap directly. A successful Intelligence (Religion) check might provide insight into the imagery displayed by a trap in a temple or shrine, giving other characters a clue about how and where to direct their efforts. A character could stand in front of a dart trap while holding a shield that the darts can target harmlessly, while other characters trigger that element as they work to disable it.

Complex Traps and Legendary Monsters
A complex trap is like a legendary monster in some ways. It has several tricks it can use on its turn, and it remains a threat throughout the round, not just on its turn. The trap's active elements are like a legendary creature's normal actions, and its constant elements are equivalent to legendary actions-except they are tied to specific areas in the trapped room.

Although a legendary creature can move, improvise actions, and so forth, a trap is set to a specific script-an aspect that has the potential to make a complex trap stale and predictable. That's where dynamic elements come in. They keep the players on their toes and make dealing with a complex trap feel like a challenging, evolving situation.