When determining the DC to notice an invisible enemy during combat, what counts as "in combat" or "not moving"?

Question

What modifiers should be applied when when determining the Perception DC to locate an invisible creature during common combat situation?

As per the Core Rulebook, the base DC is 20, and to pinpoint the exact square is another +20. There are various additional modifiers on this DC, but three that are of particular relevance to me are:

• -20 if the creature is in combat or speaking
• +20 if the creature is not moving
• -10 if the creature is moving at full speed

I'm curious exactly what constitutes as "in combat" or "not moving", as I can't seem to get a consistent answer from the rules or various discussion threads on invisibility.

Let me illustrate with a few scenarios, where we assume that a PC has cast Greater Invisibility on themselves, and a few rounds later, has attacked NPC 1. Later that round, NPC 2 (who was not attacked by the PC), wants to locate the invisible PC.

• Scenario 1: The PC begins their turn adjacent to NPC 1 and spends a full round action to attack NPC 1 before ending their turn with no other actions performed (thus did not take a move action and remained in their square). NPC 2 now tries to locate the PC.

• Scenario 2: As above, but this time the PC takes a 5-foot-step away from NPC 1 in an unknown direction after attacking. NPC 2 now tries to locate the PC.

• Scenario 3: As above, but this time the PC only uses a standard action to attack NPC 1, before taking a move action to move at their full speed away from NPC 1 in an unknown direction. NPC 2 now tries to locate the PC.

And finally, for a slightly different scenario from above

• Scenario 4: The PC is no longer performing melee attacks, and is not standing adjacent to any enemies. Instead, they begin their turn by taking a potion and drinking it. NPC 2 now tries to locate the PC.

Which modifiers would you apply in each scenario? My interpretation of the DC to pinpoint the exact square would be

• Scenario 1: In Combat, Not Moving => DC = 40 - 20 + 20 = 40
• Scenario 2: In Combat => DC = 40 - 20 = 20
• Scenario 3: In Combat, Moving at full speed => DC = 40 - 20 - 10 = 10
• Scenario 4: In Combat, Not Moving => DC = 40 - 20 + 20 = 40

However, I'm unsure if the modifiers in italics are applied correctly.

Does "Not Moving" here specifically refer to taking a move action, or is it anything other than standing completely still? Is swinging a weapon equivalent to drinking a potion when it comes to this?

Does "In Combat" specifically refer to having rolled initiative as part of an encounter? Or does it mean actively participating with aggressive actions?

Any help clarifying RAW or RAI would be appreciated.

(Note: I'm aware that in these combat situations, NPC 1 can easily locate the PC as they were the target of an attack. I'm also aware that invisibility only removes vision of the invisible creature, and that the PC could be located by other means - including environmental factors or being told by an ally to target a particular square. I'm specifically interested in the scenario where there's no additional stimulus, and another NPC is rolling perception to pinpoint the PC's location)

Answer 1

In Combat is a defined state

Per the rules, Combat is any time you're in Initiative*:

Combat is cyclical; everybody acts in turn in a regular cycle of rounds. Combat follows this sequence:
1. When combat begins, all combatants roll initiative.

*This isn't necessarily true; the GM can tell you if you are in combat, a social encounter, or in initiative for another reason

There is no option to not roll Initiative, so you are considered In Combat (although it would be a completely reasonable house-rule to go against this general ruling).

Moving is more gray, but should relate to Move actions

The game term Movement is related to moving yourself around the space. While yes, it does take "movement" to retrieve something from your invisible bag, the game system does not consider this Moving. If you're still unsure, you need only look at the other modifier you quote

+20 if the creature is not moving
-10 if the creature is moving at full speed

It would make no sense for them to use the same phrasing "creature is [...] moving" unless they're referring to the same mechanic.

Answer 2

What does Invisibility do?

According to Invisibility (which Greater Invisibility acts like), a PC that is invisible gains a +40 bonus to their Stealth roll if they are not moving, and a +20 bonus if they are. Their roll deteremines the DC, and these bonuses are not modified by being in combat.

When are you "In Combat?

Does "In Combat" specifically refer to having rolled initiative as part of an encounter? Or does it mean actively participating with aggressive actions?

I was able to find this on the srd under Combat:

When combat begins, all combatants roll initiative.

By this, we can determine that if initiative has not been rolled, you are not yet "in combat." If initiative has been rolled, you are "in combat."

When are you moving?

Does "Not Moving" here specifically refer to taking a move action, or is it anything other than standing completely still? Is swinging a weapon equivalent to drinking a potion when it comes to this?

I would lean towards RAI being "moving is moving", though reasonable minds may differ on this point. I will point to the Paralyzed condition for RAW evidence to my side:

A paralyzed character is frozen in place and unable to move or act. A paralyzed character has effective Dexterity and Strength scores of 0 and is helpless, but can take purely mental actions. A winged creature flying in the air at the time that it becomes paralyzed cannot flap its wings and falls. A paralyzed swimmer can’t swim and may drown. A creature can move through a space occupied by a paralyzed creature—ally or not. Each square occupied by a paralyzed creature, however, counts as 2 squares to move through.

While it includes two terms, "move" and "act", any action involving movement (including attacking) is disallowed by implication, while explicitly allowing purely mental actions to be taken (therefore you do not technically "lose" your actions in the turn). You also do not lose your move action for the turn, which leads me to believe that while taking a Move action is certainly moving, so is any other action involving movement.

Based on this, I would say that anything other than standing, sitting, squatting, or lying down completely still would be considered "moving". Things like your heart beating, lungs breathing, and purely mental actions are not moving. Swinging a sword is equivalent to drinking a potion in this respect. Effectively, if you cannot do it while paralyzed, it is probably moving.

Scenarios

Since all scenarios presented are turn-based, we can presume that initiative has been rolled and the PC is in combat.

Scenario 1: The PC begins their turn adjacent to NPC 1 and spends a full round action to attack NPC 1 before ending their turn with no other actions performed (thus did not take a move action and remained in their square). NPC 2 now tries to locate the PC.

I would say that even though the PC is not taking a Move action, they are "moving" to make the attacks and therefore only receive a +20 bonus to their Stealth roll.

Scenario 2: As above, but this time the PC takes a 5-foot-step away from NPC 1 in an unknown direction after attacking. NPC 2 now tries to locate the PC.

Same as above, though it is less arguable that the PC is moving. They gain a +20 to their Stealth roll.

Scenario 3: As above, but this time the PC only uses a standard action to attack NPC 1, before taking a move action to move at their full speed away from NPC 1 in an unknown direction. NPC 2 now tries to locate the PC.

Same as above, with no room to argue that the PC is not moving. The PC gains a +20 to their Stealth roll.

Scenario 4: The PC is no longer performing melee attacks, and is not standing adjacent to any enemies. Instead, they begin their turn by taking a potion and drinking it. NPC 2 now tries to locate the PC.

Under the presumption that you must move to attack, I would say you are also moving in this case and you still receive only a +20. If attacking involves moving, so must retrieving an item and drinking it.