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Perception

Your Perception measures your ability to notice things, search for what’s hidden, and tell whether something about a situation is “off.” This statistic is frequently used for rolling initiative to determine who goes first in an encounter, and for the Seek action.

You have a Perception modifier based on your Wisdom. Your class determines your proficiency in Perception.

Perception modifier = Wisdom modifier + Perception proficiency modifier + circumstance bonus + conditional bonus + item bonus + circumstance penalty + conditional penalty + item penalty + untyped penalties

In many circumstances, such as when someone’s trying to sneak past you, the GM will roll against your Perception DC. Much like skill DCs, your Perception DC is 10 plus your Perception modifier.

Light

The amount of light can affect how well you see things.

There are three levels of light: bright light, dim light, and darkness. The rules in this book are presented assuming all creatures are in bright light.

Bright Light

In bright light, creatures and objects can be seen clearly by anyone with normal vision or better. Some types of creatures are dazzled or blinded by bright light.

Dim Light

Areas in shadow or lit by weak light sources are in dim light.

Creatures and objects in dim light are concealed  to creatures that don’t have blindsense, blindsight, darkvision, or low-light vision (see Special Senses below).

Darkness

A creature or object within darkness is considered unseen to those without blindsense, blindsight, or darkvision (see Special Senses below). A creature without these senses is blinded while in darkness, though it might be able to see lit areas beyond the darkness. If a creature can see into a lit area, it can target creatures within that lit area, but it treats such targets as concealed.

Senses

The ways a creature can use Perception depend on its senses.

Precise and Imprecise Senses

A typical character has two prominent senses: vision and hearing. Vision is a precise sense: a sense that can be used to perceive the world in nuanced detail. The only way to target a creature without having drawbacks is to use a precise sense. You can usually see a creature automatically with a precise sense unless that creature is hiding or obscured by the environment, in which case you have to use the Seek action to detect the creature.

Hearing is an imprecise sense—it isn’t sufficient to make out the full range of detail that a precise sense can.

You can usually sense (see Sensed on page 303) a creature automatically with an imprecise sense, unless it’s using Stealth or in an environment that distorts the sense, such as a noisy room in the case of hearing. In those cases, you have to use the Seek action to detect the creature. At best, an imprecise sense can give a creature the sensed condition—it can’t make the creature seen.

Pathfinder’s rules assume that a given creature has vision as its only precise sense and hearing as its only imprecise sense. Other senses, such as smell, are insufficient to enable a creature to sense another in most circumstances.

Some creatures, however, have precise or imprecise senses that don’t match this assumption. For instance, an animal with the scent ability can use its sense of smell as an imprecise sense. A creature with poor vision might treat that sense as imprecise, while a creature with echolocation or a similar ability can use hearing as a precise sense. Such senses are often given special names. Poor vision might be listed as “imprecise vision,” while a specialized precise sense might appear as “echolocation” or the like.

Special Senses

While a human might have a difficult time making out creatures in dim light, an elf can see those creatures just fine. and though elves have no problem seeing on a moonlit night, their vision cannot penetrate complete darkness, whereas a dwarf’s can.

Special senses grant greater awareness that allows creatures with these senses to either ignore or reduce the effects of the unseen, sensed, or concealed conditions (described in Detecting Creatures on page 302) when it comes to situations that foil normal vision.

Blindsense

Blindsense is an imprecise sense with which a creature can detect things it can’t see, out to a specified range.

Every version of blindsense uses a particular nonvisual sense. A dragon might use its exceptional scent to smell intruders, while an undead might detect a creature’s life force or hear heartbeats. Against a creature taking precautions to avoid visual detection, a creature with blindsense treats sensed creatures as if they were concealed, and treats unseen creatures as if they were sensed. This applies only within the range of the creature’s blindsense.

Blindsight

Blindsight is a precise sense other than vision, such as echolocation, that a creature can use to perceive details in a same way a human uses vision, out to a specified range. As with blindsense, every version of blindsight is a particular nonvisual sense. Against a creature taking precautions to avoid visual detection, creatures with blindsight treat unseen creatures as if they were concealed, and concealed or sensed creatures as if they were seen. This applies only within the range of the creature’s blindsight.

Darkvision

A creature with darkvision can see perfectly well in areas of darkness and dim light, though such vision is in black and white only. Some forms of magical darkness, such as a 4th-level darkness spell, block darkvision. However, a creature with greater darkvision can see through even these forms of magical darkness.

Low-Light Vision

A creature with low-light vision does not treat creatures or objects within dim light as concealed.

Scent

Scent involves sensing creatures or objects by smell. It is an imprecise sense within its range, but it functions only if the creature or object being detected emits an aroma (for instance, incorporeal creatures usually do not exude an aroma). If a creature emits a heavy aroma or is upwind, the GM can double or even triple the range of scent abilities used to detect that creature, and the GM can reduce the range if a creature is downwind. In essence, scent is equivalent to blindsense via scent.

Tremorsense

Tremorsense allows a creature to feel the vibrations caused by movement through a solid surface. It is an imprecise sense within its range, but it functions only if both the detecting and the target creatures are on or in the same surface and the target creatures are moving along (or burrowing through) it. In essence, tremorsense is equivalent to blindsense via detecting tremors.

Detecting Creatures

There are four states that measure the degree to which you can sense a creature: seen, concealed, sensed, and unseen. When you’re trying to target a creature that’s harder to see or otherwise sense, various drawbacks apply. Most of these rules apply to objects you’re trying to detect as well as creatures.

Typically, the GM tracks how well creatures can detect one another, since neither party has perfect information.

For example, you might think a creature is in the last place you sensed it, but it was actually able to Sneak away. Or you might think a creature can’t see you in the darkness, but it has darkvision.

You can attempt to avoid detection by using the Stealth skill to Hide or Sneak or by using Deception to Create a Diversion.

Seen

In most circumstances, you can see creatures without difficulty and target them normally, but various situations might make targeting more difficult. If you can’t, you’ll need to factor in the targeting restrictions that follow. See the Detecting with Other Senses sidebar for advice regarding creatures that don’t use sight as their primary sense.

Concealed

A creature is concealed from you if it’s in mist, within dim light, or amid something else that obscures sight but does not provide a physical barrier to effects. An effect or type of terrain that describes an area of concealment makes all creatures within it concealed.

When you target a creature that’s concealed from you, before you roll to determine your effect, you must attempt a DC 5 flat check. If you fail that check, you don’t affect the target. Sometimes the level of concealment is so great that a creature is considered merely sensed instead of seen and concealed.

Sensed

A creature that’s sensed is only barely perceptible. You know what space the sensed creature occupies, but little else. Perhaps the creature just moved behind cover and successfully used the Hide action. Maybe you’ve been blinded or the creature is under the effects of invisibility, but you used Seek to determine its general location based on hearing alone. Your target might be in a deep fogbank or behind a waterfall, where you can see some movement but can’t determine an exact location.

When targeting a creature that you sense, before you roll to determine your effect, you must attempt a DC 11 flat check. If you fail that check, you don’t affect the target. You’re still flat-footed to the creature whether you successfully target it or not.

Unseen

If a creature is unseen, you have no idea where it is. You don’t know what space it occupies, you’re flat-footed to it, and you can’t easily target it with attacks or targeted spells and affects. Using the Seek action can help you detect an unseen creature, usually making it sensed.

Targeting an unseen creature is difficult. However, if you suspect there’s a creature around, you can pick a square and attempt an attack. This works like targeting a sensed creature, but the flat check and attack roll are rolled in secret by the GM. The GM won’t tell you if you missed due to failing the flat check, rolling an insufficient attack roll, or choosing the wrong square.

For instance, suppose an enemy elf wizard became invisible and then Sneaked away. You suspect that with the elf’s Speed of 30 feet, he probably moved 15 feet toward an open door. You move up and attack a space 15 feet from where the elf started and directly on the path to the door.

The GM secretly rolls an attack roll and flat check, but she knows that you were not quite correct—the elf was actually in the adjacent space! She tells you that you missed, so you decide to make your next attack on the adjacent space, just in case. This time, it’s the right space and the GM’s secret attack roll and flat check both succeed, so you hit!

Invisible

A creature that’s invisible (by way of the invisibility spell, a ring of invisibility, or some other magic item, spell effect, or special ability) is automatically unseen to everyone.

You can use the Seek action to attempt to detect an invisible creature, making it sensed to you on a successful Perception check. This lasts until the invisible creature uses Sneak to become unseen again. If the creature becomes invisible while seen by you, it starts out sensed, since you know where it was when it became invisible, though it can proceed to Sneak after becoming invisible to become unseen.

Other effects might make an invisible creature sensed or even concealed. For instance, if you were tracking an invisible creature’s footprints through the snow, the footprints would make it sensed, and throwing a net over an invisible creature would make it

Detecting With Other Senses

If a monster uses a sense other than vision as a precise sense, the GM can adapt the system for detecting creatures to equivalents that work with those senses. For example, a creature that has echolocation might use hearing as a primary sense, treating creatures as “heard” if it can directly hear them, concealed if they’re in a noisy chamber, sensed if it has located them, and “unheard” if it can’t hear their location at all. Many abilities that apply when a creature is unseen would still apply if it were unheard, though the GM might determine ones that are explicitly visual in nature don’t.

using sTealTh wiTh oTher senses

The Stealth skill is designed to use Hide for avoiding visual detection and Sneak to avoid being heard. For many special senses, a player can describe how they’re avoiding detection by a special sense and use the most applicable Stealth action. For instance, a creature stepping lightly to avoid being detected via tremorsense would be using Sneak. A character using Stealth in this way overrides the usual rules by which special senses detect creatures. For instance, when you successfully Hide from a creature with blindsight, it treats you as sensed as normal for the Hide action instead of treating you as seen as it normally does for sensed creatures.

In some cases, rolling a Dexterity-based Stealth skill check doesn’t make the most sense. For example, when facing a monster that can detect heartbeats, to avoid being detected a PC might need to meditate to slow their heart rate, using Wisdom instead of Dexterity as the ability modifier for the Stealth check. When going up against multiple senses, such as if the monster could also hear or see, the PC would use the lowest applicable ability modifier for her check.