Any character in the Pathfinder role-playing game can, after preparing with a few skills and feats, take a one-level dip into the Shadowdancer prestige class to gain the supernatural ability Hide in Plain Sight.
This ability is worded clearly and succinctly. But it requires a careful inspection of many Pathfinder core rules to fully understand it. And, unfortunately, the rules are not complete. The GM will need to make a few "house rules".
This essay explains the Hide in Plain Sight ability. What does it really do? What "house rules" are needed?
Thanks go to the contributors of Paizo forum topics for rounding up which issues need discussion.
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The word "area" is undefined in the rulebook, but because of the chapter on combat it is strongly implied that during the rules about vision and light an "area" is a five-foot square. Thus each map square has an objective light level based only upon the light sources.
Whether or not someone with Darkvision is nearby is irrelevant. Darkvision allows seeing in places that have Dim Light or Darkness. But Darkvision does not cause flashlight-beams to shine from a creature's eyes to illuminate the map squares.
The rules about vision and light list three official examples of Dim Light.
Areas of dim light include outside at night with a moon in the sky, bright starlight, and the area between 20 and 40 feet from a torch.
A forum post from designer James Jacobs adds shadows as a fourth official example of Dim Light. Since light levels apply to five-foot map squares, these shadows need to be large enough to dominate a map square.
House Rule Needed: How much of a map square must be in shadow for that map square to count as Dim Light?
This is probably a simple house rule because creatures and objects have a substantial size change from Medium to Large. So a sensible rule is that the shadow of a Large creature suffices, but not the shadow of a medium creature. Similarly, an object should fill at least two map squares to cast a sufficiently large shadow.
The Stealth skill description is badly worded, but quite clear. To use Stealth usually requires two prerequisites.
Note that the second does not imply the first. A character standing in a field in moonlight has concealment but is quite observable. A character shooting through a wall's arrow slit has total cover but is slightly observable through the slit.
The super-hiding abilities from Shadow Sorcerer and Ranger explicitly mention both of these stealth prerequisites.
Shadow Well (Sp): At 9th level, you can use the Stealth skill even while being observed and without cover or concealment, as long as you are within 10 feet of a shadow other than your own. In addition...
Camouflage (Ex): A ranger of 12th level or higher can use the Stealth skill to hide in any of his favored terrains, even if the terrain doesn't grant cover or concealment.
Hide in Plain Sight (Ex): While in any of his favored terrains, a ranger of 17th level or higher can use the Stealth skill even while being observed
Unfortunately, the Hide in Plain Sight ability for the Shadowdancer and Assassin are not worded as carefully. But they also attempt to mention both prerequisites.
Hide in Plain Sight (Su): A shadowdancer can use the Stealth skill even while being observed. As long as she is within 10 feet of an area of dim light, a shadowdancer can hide herself from view in the open without anything to actually hide behind. She cannot, however, hide in her own shadow.
Hide in Plain Sight (Su): At 8th level, an assassin can use the Stealth skill even while being observed. As long as he is within 10 feet of some sort of shadow, an assassin can hide himself from view in the open without having anything to actually hide behind. He cannot, however, hide in his own shadow.
Specifically, both character classes can always use Stealth when being observed. They are exempt from that prerequisite.
If they are also within 10' of a map square with Dim Light then they are also exempt from the other prerequisite about needing either cover or concealment.
Note that Blindsight does trump Stealth (and thus Hide in Plain Sight), just as any sufficient Perception skill roll does.
Combat is considered "distracting" in the rules about magic use. So most GMs consider combat "distracting" enough to provide a -5 penalty to Perception skill rolls. This can be a big aid to using Hide in Plain Sight during combat!
House Rule Needed: Is combat "distracting" for Perception skill use?
Successfully hiding because of Stealth is a different condition than being Invisible. But the combat rules do not mention how hiding aids attacks. Most GMs extend the three rules for being invisible to character attacking from hiding.
House Rule Needed: Is attacking from hiding the same as attacking while invisible?
In the Paizo forums most GMs agree that a defender who "puts his money where his mouth is" by readying an attack that will trigger when the hiding attacker becomes visible gains two benefits:
How much movement is needed to use Stealth? The rules for Stealth do not say!
This is a huge issue. Can a melee character make a full attack and then disappear into the shadows? Can a Witch cast a spell, Cackle, and then vanish into the shadows?
Most GMs allow this, because in D&D 3.5e it was indeed possible to use Stealth with a five-foot step. There was a feat called Cunning Evasion that made use of that fact.
House Rule Needed: Can Stealth be used during a five-foot step? Or is a move action required?
Does someone using Stealth gain any cover or concealment from their hiding? Any character could use Stealth with only one of those conditions: does it gain the other? And characters with Hide in Plain Sight near a map square of Dim Light might not have either condition: does it gain either or both?
The rules about concealment state when Total Concealment happens.
If you have line of effect to a target but not line of sight, he is considered to have total concealment from you.
So anytime an opponent knows which map square you are hiding in, but does not know your precise location, you have Total Concealment. This could happen because of Blindsense or Tremorsense. Or it could happen if the character trying to hide partly reveals his or her location.
This is the most gaping hole in the rules about hiding. It makes sense that some actions would reveal a hiding character's approximate location, and others would completely end the use of Stealth. But the GM needs to make the distinction clear.
House Rule Needed: Which actions partly or totally end Stealth?
For example, perhaps casting a spell with a Vocal component but without a Somatic component causes opponents to know your map square but not your precise location (so you have Total Concealment) but casting a spell with a Somatic component ends Stealth.
According to the Paizo forums, the most common house rule is to mimic the Invisibility spell for game balance purposes. Any directly offensive action ends Stealth completely. Any defensive or indirect action (for example, casting a healing, buff, or summon spell) does not ruin Stealth at all. Borderline effects, such as a Witch's Cackle hex, cause opponents to know your map square but not your precise location (so you have Total Concealment).
Why can't a spell caster use the Blur spell as a cheap version of Hide in Plain Sight? Blur grants concealment but does not nullify the other prerequisite for using Stealth: not being observed. (Note, however, that a Shadowdancer or Assassin with Blur could use Stealth, since their Hide in Plain Sight ability does indeed completely nullify the other prerequisite.)
Why does the rulebook bother to mention that a Shadowdancer and Assassin cannot hide in his own shadow? This restriction prevents a player from saying, "I'll use Enlarge Person on myself, so my shadow covers more than a map square, so I can use Hide in Plain Sight". That would be nonsensical!
Can a Shadowdancer or Assasin use Hide in Plain Sight in the light level named Darkness? Probably not. Both classes are tied to shadow, and the light level Darkness isn't shadow. Ironically, in an underground dungeon or a warehouse without windows both characters would benefit from the Light or Dancing Lights cantrips to make some map squares Dim Light instead of Darkness.
Darkvision does not help see anyone using Stealth. Whether that use of Stealth came from Hide in Plain Sight or not seems irrelevant to the rules. After all, someone using Hide in Plain Sight can be standing in the open in a brightly lit map square, as long as a map square of Dim Light is nearby.
Supernatural abilities do not produce magical auras. So the Detect Magic cantrip does not show a Shadowdancer (or Assassin) using the Hide in Plain Sight ability to enter Stealth.
Similarly, the Detect Magic cantrip does not normally help see a character currently hiding with Stealth. (Someone hiding behind a rock does not worry about his or her magic armor's aura shining out past the rock's edge.) Exemption from the conver/concealmeant requirement through Hide in Plain Sight should not allow Detect Magic to automatically spot the hiding character.
Touch attacks always ignore the Armor bonus, Shield bonus, and Natural Armor bonus to AC. This means that a character that is invisibile, making a touch attack, considers only a very small portion of the target's AC. (All that is left is "AC = 10 + Size Bonus + Deflection Bonus".) A character attacking from hiding probably has a similarly easy time making touch attacks.