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Traps

Source PRPG Core Rulebook pg. 416
Traps are a common danger in dungeon environments. From gouts of white-hot flame to hails of poisoned darts, traps can serve to protect valuable treasure or stop intruders from proceeding.

Elements of a Trap

Source PRPG Core Rulebook pg. 416
All traps—mechanical or magical—have the following elements: CR, type, Perception DC, Disable Device DC, trigger, reset, and effect. Some traps might also include optional elements, such as poison or a bypass. These characteristics are described below.

Type

Source PRPG Core Rulebook pg. 416
A trap can be either mechanical or magical in nature.

Mechanical: Dungeons are frequently equipped with deadly mechanical (nonmagical) traps. A trap typically is defined by its location and triggering conditions, how hard it is to spot before it goes off, how much damage it deals, and whether or not the characters receive a saving throw to mitigate its effects. Traps that attack with arrows, sweeping blades, and other types of weaponry make normal attack rolls, with specific attack bonuses dictated by the trap’s design. A mechanical trap can be constructed by a PC through successful use of the Craft (traps) skill (see Designing a Trap on page 423 and the skill description on page 91).

Creatures that succeed on a Perception check detect a trap before it is triggered. The DC of this check depends on the trap itself. Success generally indicates that the creature has detected the mechanism that activates the trap, such as a pressure plate, odd gears attached to a door handle, and the like. Beating this check by 5 or more also gives some indication of what the trap is designed to do.

Magic: Many spells can be used to create dangerous traps. Unless the spell or item description states otherwise, assume the following to be true.

  • A successful Perception check (DC 25 + spell level) detects a magic trap before it goes off.
  • Magic traps permit a saving throw in order to avoid the effect (DC 10 + spell level × 1.5).
  • Magic traps may be disarmed by a character with the trapfinding class feature with a successful Disable Device skill check (DC 25 + spell level). Other characters have no chance to disarm a magic trap with a Disable Device check.
Magic traps are further divided into spell traps and magic device traps. Magic device traps initiate spell effects when activated, just as wands, rods, rings, and other magic items do. Creating a magic device trap requires the Craft Wondrous Item feat.

Spell traps are simply spells that themselves function as traps. Creating a spell trap requires the services of a character who can cast the needed spell or spells, who is usually either the character creating the trap or an NPC spellcaster hired for that purpose.

Perception and Disable Device DCs

Source PRPG Core Rulebook pg. 417
The builder sets the Perception and Disable Device DCs for a mechanical trap. For a magic trap, the values depend on the highest-level spell used.

Mechanical Trap: The base DC for both Perception and Disable Device checks is 20. Raising or lowering either of these DCs affects the CR (Table 13–3).

Magic Trap: The DC for both Perception and Disable Device checks is equal to 25 + the spell level of the highestlevel spell used. Only characters with the trapfinding class feature can attempt a Disable Device check involving a magic trap.

Trigger

Source PRPG Core Rulebook pg. 417
A trap’s trigger determines how it is sprung.

Location: A location trigger springs a trap when someone stands in a particular square.

Proximity: This trigger activates the trap when a creature approaches within a certain distance of it. A proximity trigger differs from a location trigger in that the creature need not be standing in a particular square. Creatures that are flying can spring a trap with a proximity trigger but not one with a location trigger. Mechanical proximity triggers are extremely sensitive to the slightest change in the air. This makes them useful only in places such as crypts, where the air is unusually still.

The proximity trigger used most often for magic device traps is the alarm spell. Unlike when the spell is cast, an alarm spell used as a trigger can have an area that’s no larger than the area the trap is meant to protect. Some magic device traps have special proximity triggers that activate only when certain kinds of creatures approach. For example, a detect good,/i> spell can serve as a proximity trigger on an evil altar, springing the attached trap only when someone of good alignment gets close enough to it.

Sound: This trigger springs a magic trap when it detects any sound. A sound trigger functions like an ear and has a +15 bonus on Perception checks. A successful Stealth check, magical silence, and other effects that would negate hearing defeat it. A trap with a sound trigger requires the casting of clairaudience during its construction.

Visual: This trigger for magic traps works like an actual eye, springing the trap whenever it “sees” something. A trap with a visual trigger requires the casting of arcane eye, clairvoyance, or true seeing during its construction. Sight range and the Perception bonus conferred on the trap depend on the spell chosen, as shown.
SpellSight RangesPerception Bonus
Arcane eyeLine of sight (unlimited range)+20
ClairvoyanceOne preselected location+15
True seeingLine of sight (up to 120 ft.)+30
If you want the trap to see in the dark, you must either choose the true seeing option or add darkvision to the trap as well. (Darkvision limits the trap’s sight range in the dark to 60 feet.) If invisibility, disguises, or illusions can fool the spell being used, they can fool the visual trigger as well.

Touch: A touch trigger, which springs the trap when touched, is one of the simplest kinds of trigger to construct. This trigger may be physically attached to the part of the mechanism that deals the damage or it may not. You can make a magic touch trigger by adding alarm to the trap and reducing the area of the effect to cover only the trigger spot.

Timed: This trigger periodically springs the trap after a certain duration has passed.

Spell: All spell traps have this kind of trigger. The appropriate spell descriptions explain the trigger conditions for traps that contain spell triggers.

Duration

Source PRPG Core Rulebook pg. 417
Unless otherwise stated, most traps have a duration of instantaneous; once triggered, they have their effect and then stop functioning. Some traps have a duration measured in rounds. Such traps continue to have their listed effect each round at the top of the initiative order (or whenever they were activated, if they were triggered during combat).

Reset

Source PRPG Core Rulebook pg. 417
A reset element is the set of conditions under which a trap becomes ready to trigger again. Resetting a trap usually takes only a minute or so. For a trap with a more difficult reset method, you should set the time and labor required.

No Reset: Short of completely rebuilding the trap, there’s no way to trigger it more than once. Spell traps have no reset element.

Repair: To get the trap functioning again, you must repair it. Repairing a mechanical trap requires a Craft (traps) check against a DC equal to the one for building it. The cost for raw materials is one-fifth of the trap’s original market price. To calculate how long it takes to fix a trap, use the same calculations you would for building it, but use the cost of the raw materials required for repair in place of the market price.

Manual: Resetting the trap requires someone to move the parts back into place. This is the kind of reset element most mechanical traps have.

Automatic: The trap resets itself, either immediately or after a timed interval. Bypass (Optional Element) If the builder of a trap wants to be able to move past the trap after it is created or placed, it’s a good idea to build in a bypass mechanism: something that temporarily disarms the trap. Bypass elements are typically used only with mechanical traps; spell traps usually have built-in allowances for the caster to bypass them.

Lock: A lock bypass requires a DC 30 Disable Device check to open.

Hidden Switch: A hidden switch requires a DC 25 Perception check to locate.

Hidden Lock: A hidden lock combines the features above, requiring a DC 25 Perception check to locate and a DC 30 Disable Device check to open. Effect The effect of a trap is what happens to those who spring it. This often takes the form of either damage or a spell effect, but some traps have special effects. A trap usually either makes an attack roll or forces a saving throw to avoid it. Occasionally a trap uses both of these options, or neither (see Never Miss).

Pits: These are holes (covered or not) that characters can fall into, causing them to take damage. A pit needs no attack roll, but a successful Reflex save (DC set by the builder) avoids it. Other save-dependent mechanical traps also fall into this category. Falling into a pit deals 1d6 points of damage per 10 feet of depth.

Pits in dungeons come in three basic varieties: uncovered, covered, and chasms. Pits and chasms can be defeated by judicious application of the Acrobatics skill, the Climb skill, or various mechanical or magical means.

Uncovered pits and natural chasms serve mainly to discourage intruders from going a certain way, although they cause much grief to characters who stumble into them in the dark, and they can greatly complicate nearby melee.

Covered pits are much more dangerous. They can be detected with a DC 20 Perception check, but only if the character is taking the time to carefully examine the area before walking across it. A character who fails to detect a covered pit is still entitled to a DC 20 Reflex save to avoid falling into it. If she was running or moving recklessly at the time, however, she gets no saving throw and falls automatically.

Trap coverings can be as simple as piled refuse (straw, leaves, sticks, garbage), a large rug, or an actual trap door concealed to appear as a normal part of the floor. Such a trap door usually swings open when enough weight (usually about 50 to 80 pounds) is placed upon it. Devious trap builders sometimes design trap doors so they spring back shut after they open. The trap door might lock once it’s back in place, leaving the stranded character well and truly trapped. Opening such a trap door is just as difficult as opening a regular door (assuming the trapped character can reach it), and a DC 13 Strength check is needed to keep a spring-loaded door open.

Pit traps often have something nastier than just a hard floor at the bottom. A trap designer might put spikes, monsters, or a pool of acid, lava, or even water at the bottom. For rules on pit spikes and other such add-ons, see the Miscellaneous Trap Features section.

Monsters sometimes live in pits. Any monster that can fit into the pit might have been placed there by the dungeon’s designer, or might simply have fallen in and not been able to climb back out.

A secondary trap, mechanical or magical, at the bottom of a pit can be particularly deadly. Activated by a falling victim, the secondary trap attacks the already injured character when she’s least ready for it.

Ranged Attack Traps: These traps f ling darts, arrows, spears, or the like at whomever activated the trap. The builder sets the attack bonus. A ranged attack trap can be configured to simulate the effect of a composite bow with a high Strength rating, which provides the trap with a bonus on damage equal to its Strength rating. These traps deal whatever damage their ammunition normally does. If a trap is constructed with a high Strength rating, it has a corresponding bonus on damage.

Melee Attack Traps: These traps feature such obstacles as sharp blades that emerge from walls and stone blocks that fall from ceilings. Once again, the builder sets the attack bonus. These traps deal the same damage as the melee weapons they “wield.” In the case of a falling stone block, you can assign any amount of bludgeoning damage you like, but remember that whoever resets the trap has to lift that stone back into place.

A melee attack trap can be constructed with a built-in bonus on damage rolls, just as if the trap itself had a high Strength score.

Spell Traps: Spell traps produce the spell’s effect. Like all spells, a spell trap that allows a saving throw has a save DC of 10 + spell level + caster’s relevant ability modifier.

Magic Device Traps: These traps produce the effects of any spells included in their construction, as described in the appropriate entries. If the spell in a magic device trap allows a saving throw, its save DC is (10 + spell level) × 1.5. Some spells make attack rolls instead.

Special: Some traps have miscellaneous features that produce special effects, such as drowning for a water trap or ability damage for poison. Saving throws and damage depend on the poison or are set by the builder, as appropriate.

Bypass (Optional Element)

Source PRPG Core Rulebook pg. 418
If the builder of a trap wants to be able to move past the trap after it is created or placed, it’s a good idea to build in a bypass mechanism: something that temporarily disarms the trap. Bypass elements are typically used only with mechanical traps; spell traps usually have built-in allowances for the caster to bypass them.

Lock: A lock bypass requires a DC 30 Disable Device check to open.

Hidden Switch: A hidden switch requires a DC 25 Perception check to locate.

Hidden Lock: A hidden lock combines the features above, requiring a DC 25 Perception check to locate and a DC 30 Disable Device check to open.

Effect

Source PRPG Core Rulebook pg. 418
The effect of a trap is what happens to those who spring it. This often takes the form of either damage or a spell effect, but some traps have special effects. A trap usually either makes an attack roll or forces a saving throw to avoid it. Occasionally a trap uses both of these options, or neither (see Never Miss).

Pits: These are holes (covered or not) that characters can fall into, causing them to take damage. A pit needs no attack roll, but a successful Reflex save (DC set by the builder) avoids it. Other save-dependent mechanical traps also fall into this category. Falling into a pit deals 1d6 points of damage per 10 feet of depth.

Pits in dungeons come in three basic varieties: uncovered, covered, and chasms. Pits and chasms can be defeated by judicious application of the Acrobatics skill, the Climb skill, or various mechanical or magical means.

Uncovered pits and natural chasms serve mainly to discourage intruders from going a certain way, although they cause much grief to characters who stumble into them in the dark, and they can greatly complicate nearby melee.

Covered pits are much more dangerous. They can be detected with a DC 20 Perception check, but only if the character is taking the time to carefully examine the area before walking across it. A character who fails to detect a covered pit is still entitled to a DC 20 Reflex save to avoid falling into it. If she was running or moving recklessly at the time, however, she gets no saving throw and falls automatically.

Trap coverings can be as simple as piled refuse (straw, leaves, sticks, garbage), a large rug, or an actual trap door concealed to appear as a normal part of the floor. Such a trap door usually swings open when enough weight (usually about 50 to 80 pounds) is placed upon it. Devious trap builders sometimes design trap doors so they spring back shut after they open. The trap door might lock once it’s back in place, leaving the stranded character well and truly trapped. Opening such a trap door is just as difficult as opening a regular door (assuming the trapped character can reach it), and a DC 13 Strength check is needed to keep a spring-loaded door open.

Pit traps often have something nastier than just a hard floor at the bottom. A trap designer might put spikes, monsters, or a pool of acid, lava, or even water at the bottom. For rules on pit spikes and other such add-ons, see the Miscellaneous Trap Features section.

Monsters sometimes live in pits. Any monster that can fit into the pit might have been placed there by the dungeon’s designer, or might simply have fallen in and not been able to climb back out.

A secondary trap, mechanical or magical, at the bottom of a pit can be particularly deadly. Activated by a falling victim, the secondary trap attacks the already injured character when she’s least ready for it.

Ranged Attack Traps: These traps f ling darts, arrows, spears, or the like at whomever activated the trap. The builder sets the attack bonus. A ranged attack trap can be configured to simulate the effect of a composite bow with a high Strength rating, which provides the trap with a bonus on damage equal to its Strength rating. These traps deal whatever damage their ammunition normally does. If a trap is constructed with a high Strength rating, it has a corresponding bonus on damage.

Melee Attack Traps: These traps feature such obstacles as sharp blades that emerge from walls and stone blocks that fall from ceilings. Once again, the builder sets the attack bonus. These traps deal the same damage as the melee weapons they “wield.” In the case of a falling stone block, you can assign any amount of bludgeoning damage you like, but remember that whoever resets the trap has to lift that stone back into place.

A melee attack trap can be constructed with a built-in bonus on damage rolls, just as if the trap itself had a high Strength score.

Spell Traps: Spell traps produce the spell’s effect. Like all spells, a spell trap that allows a saving throw has a save DC of 10 + spell level + caster’s relevant ability modifier.

Magic Device Traps: These traps produce the effects of any spells included in their construction, as described in the appropriate entries. If the spell in a magic device trap allows a saving throw, its save DC is (10 + spell level) × 1.5. Some spells make attack rolls instead.

Special: Some traps have miscellaneous features that produce special effects, such as drowning for a water trap or ability damage for poison. Saving throws and damage depend on the poison or are set by the builder, as appropriate.

Miscellaneous Trap Features

Source PRPG Core Rulebook pg. 419
Some traps include optional features that can make them considerably more deadly. The most common features are discussed below.

Alchemical Item: Mechanical traps might incorporate alchemical devices or other special substances or items, such as tanglefoot bags, alchemist’s fire, thunderstones, and the like. Some such items mimic spell effects. If the item mimics a spell effect, it increases the CR as shown on Table 13–3: CR Modifiers for Mechanical Traps.

Gas: With a gas trap, the danger is in the inhaled poison it delivers. Traps employing gas usually have the never miss and onset delay features.

Liquid: Any trap that involves a danger of drowning is in this category. Traps employing liquid usually have the never miss and onset delay features.

Multiple Targets: Traps with this feature can affect more than one character.

Never Miss: When the entire dungeon wall moves to crush you, your quick reflexes won’t help, since the wall can’t possibly miss. A trap with this feature has neither an attack bonus nor a saving throw to avoid, but it does have an onset delay. Most traps involving liquid or gas are of the never miss variety.

Onset Delay: An onset delay is the amount of time between when the trap is sprung and when it deals damage. A never miss trap always has an onset delay.

Poison: Traps that employ poison are deadlier than their nonpoisonous counterparts, so they have correspondingly higher CRs. To determine the CR modifier for a given poison, consult Table 13–3. Only injury, contact, and inhaled poisons are suitable for traps; ingested types are not. Some traps simply deal the poison’s damage. Others deal damage with ranged or melee attacks as well. See page 557 for more information on poison.

Pit Spikes: Treat spikes at the bottom of a pit as daggers, each with a +10 attack bonus. The damage bonus for each spike is +1 per 10 feet of pit depth (to a maximum of +5). Each character who falls into the pit is attacked by 1d4 spikes. This damage is in addition to any damage from the fall itself, and the statistics presented above are merely the most common variant—some traps might have far more dangerous spikes at their bottom. Pit spikes add to the average damage of the trap (see Average Damage, below).

Pit Bottom: If something other than spikes waits at the bottom of a pit, it’s best to treat that as a separate trap (see Multiple Traps) with a location trigger that activates on any significant impact, such as a falling character.

Touch Attack: This feature applies to any trap that needs only a successful touch attack (melee or ranged) to hit.

Sample Traps

Source PRPG Core Rulebook pg. 420
Nethys Note: Coming Soon

Designing a Trap

Source PRPG Core Rulebook pg. 423
Designing new traps is a simple process. Start by deciding what type of trap you want to create. Mechanical Traps: Simply select the elements you want the trap to have and add up the adjustments to the trap’s Challenge Rating that those elements require (see Table 13–3) to arrive at the trap’s final CR. From the CR you can derive the DC of the Craft (traps) checks a character must make to construct the trap (see page 424). Magic Traps: As with mechanical traps, decide what elements you want and then determine the CR of the resulting trap (see Table 13–4). If a player character wants to design and construct a magic trap, he, or an ally, must have the Craft Wondrous Item feat. In addition, he must be able to cast the spell or spells that the trap requires—or he must be able to hire an NPC to cast the spells for him.

Table 13-3: CR Modifiers for Mechanical Traps

FeatureCR Modifier
Perception DC
15 or lower-1
16-20
21-25+1
26-29+2
30 or higher+3
Disable Device DC
15 or lower-1
16-20
21-25+1
26-29+2
30 or higher+3
Reflex Save DC (Pit or Other Save-Dependent Trap
15 or lower-1
16-20
21-25+1
26-29+2
30 or higher+3
Attack Bonus (Melee or Ranged Attack Trap)
+0 or lower-2
+1 to +5-1
+6 to +10
+11 to +15+1
+16 to +20+2
Touch attack+1
Damage/Effect
Average damage+1 per 10 points of average damage
Miscellaneous Features
Alchemical deviceLevel of spell mimicked
Automatic reset+1
Liquid+5
Multiple targets (non-damage)+1
Never miss+2
Proximity or visual trigger+1
PoisonCR of poison
Black adder venom+1
Black lotus extract+8
Bloodroot+1
Blue whinnis+1
Burnt othur fumes+6
Deathblade+5
Dragon bile+6
Giant wasp poison+3
Greenblood oil+1
Insanity mist+4
Large scorpion venom+3
Malyass root paste+3
Medium spider venom+2
Nitharit+4
Purple worm poison+4
Sassone leaf residue+3
Shadow essence+3
Small centipede poison+1
Terinav root+5
Ungol dust+3
Wyvern poison+5

Table 13-4: CR Modifiers for Magic Traps

FeatureCR Modifier
Highest-level spell effect+Spell level
Damaging spell effect+1 per 10 points of average damage

Challenge Rating of a Trap

Source PRPG Core Rulebook pg. 423
To calculate the Challenge Rating of a trap, add all the CR modifiers (see Table 13–3 or Table 13–4) to the base CR for the trap type.

Mechanical Trap: The base CR for a mechanical trap is 0. If your final CR is 0 or lower, add features until you get a CR of 1 or higher.

Magic Trap: For a spell trap or magic device trap, the base CR is 1. The highest-level spell used modifies the CR (see Table 13–4).

Average Damage: If a trap (mechanical or magical) does hit point damage, calculate the average damage for a successful hit and round that value to the nearest multiple of 10. If the trap is designed to hit more than one target, multiply this value by 2. If the trap is designed to deal damage over a number of rounds, multiply this value by the number of rounds the trap will be active (or the average number of rounds, if the duration is variable). Use this value to adjust the Challenge Rating of the trap, as indicated on Table 13–3. Damage from poison does not count toward this value, but extra damage from pit spikes and multiple attacks does.

For a magic trap, only one modifier applies to the CR— either the level of the highest-level spell used in the trap, or the average damage figure, whichever is larger.

Multiple Traps: If a trap is really two or more connected traps that affect approximately the same area, determine the CR of each one separately.

Multiple Dependent Traps: If one trap depends on the success of the other (that is, you can avoid the second trap by not falling victim to the first), characters earn XP for both traps by defeating the first one, regardless if the second one is also sprung.

Multiple Independent Traps: If two or more traps act independently (they do not depend on one another to activate), characters only earn XP for traps that they defeat.

Mechanical Trap Cost

Source PRPG Core Rulebook pg. 423
The cost of a mechanical trap is 1,000 gp × the trap’s Challenge Rating. If the trap uses spells in its trigger or reset, add those costs separately. If the trap cannot be reset, divide the cost in half. If the trap has an automatic reset, increase the cost by half (+50%). Particularly simple traps, such as pit traps, might have a greatly reduced cost, subject to GM discretion. Such traps might cost as little as 250 gp × the trap’s Challenge Rating.

After you’ve determined the cost by Challenge Rating, add the price of any alchemical items or poison you incorporated into the trap. If the trap uses one of these elements and has an automatic reset, multiply the poison or alchemical item cost by 20 to provide an adequate supply of doses.

Multiple Traps: If a trap is really two or more connected traps, determine the final cost of each separately, then add those values together. This holds for both multiple dependent and multiple independent traps.

Magic Device Trap Cost

Source PRPG Core Rulebook pg. 423
Building a magic device trap involves the expenditure of gp and requires the services of a spellcaster. Table 13–5 summarizes the cost information for magic device traps. If the trap uses more than one spell (for instance, a sound or visual trigger spell in addition to the main spell effect), the builder must pay for them all (except alarm, which is free unless it must be cast by an NPC).

The costs derived from Table 13–5 assume that the builder is casting the necessary spells himself (or perhaps some other PC is providing the spells for free). If an NPC spellcaster must be hired to cast them, those costs must be factored in as well (see Chapter 6).

A magic device trap takes 1 day to construct per 500 gp of its cost.

Table 13-5: Cost Modifiers for Magic Device Traps

FeatureCost Modifier
Alarm spell used in trigger
One-Shot Trap
 Each spell used+50 gp × caster level × spell level
 Material components+ material component costs
Automatic Reset Trap
 Each spell used+50 gp × caster level × spell level
 Material components+material component costs × 100

Spell Trap Cost

Source PRPG Core Rulebook pg. 423
A spell trap has a cost only if the builder must hire an NPC spellcaster to cast it.

Craft DCs for Mechanical Traps

Source PRPG Core Rulebook pg. 423
Once you know the Challenge Rating of a trap, determine the Craft (traps) DC by referring to the values and modifiers given on Table 13–6.

Making the Checks: To determine how much progress a character makes on building a trap each week, that character makes a Craft (traps) check. See the Craft skill description for details on Craft checks and the circumstances that can affect them.

Table 13-6: Craft (Traps) DCs

Trap CRBase Craft (Traps) DC
1-520
6-1025
11-1530
16+35
Additional ComponentsModifier to Craft (Traps) DC
Proximity trigger+5
Automatic reset+5