Entering the square of an invisible enemy (occupying the same space)

[Jason Horton]

This is the situation: A drow enters the space of an invisible and hidden wayang ninja without detecting him. The ninja has the option of striking the drow with an attack of opportunity but, reasoning that they'll do more damage with two weapon fighting and a full attack later, opts not to.

If the drow had continued his movement this wouldn't be a question but the drow finishes his movement in the same square as the wayang.

RAW says that you can't occupy the same square. Core p194: "Accidentally Ending Movement in an Illegal Space:
Sometimes a character ends its movement while moving through a space where it’s not allowed to stop. When that happens, put your miniature in the last legal position you occupied, or the closest legal position, if there’s a legal position that’s closer."

The wayang ninja had three options:
1) Maintain invisibility and move out of his way;
2) Maintain invisibility and block him by standing still (not an attack on his part so invisibility is unaffected);
3) Make an attack of opportunity and lose invisibility.

The wayang ninja chose to actively avoid the drow and the drow who was unaware of the wayang ninja.

The GM ruled that the wayang ninja would move to the nearest unoccupied square for free but the option of squeezing into the same square was bandied around.

How would you rule on this?

[Kasoh]

I used to let people detect invisible creatures by moving into every square in the room if they had the movement for it where I would tell them, "You can't enter that square."

Nowadays I treat it like an unintentional overrun. The invis character can choose to step aside or make the attack of opportunity, but it must do one or the other. I'd also probably call moving out of the way an immediate action too.

I have no idea where any of that falls into the rules.

[Ryze Kuja]

Combat wrote:

Moving Through a Square

You can move through an unoccupied square without difficulty in most circumstances. Difficult terrain and a number of spell effects might hamper your movement through open spaces.

Friend

You can move through a square occupied by a friendly character, unless you are charging. When you move through a square occupied by a friendly character, that character doesn’t provide you with cover.

Opponent

You can’t move through a square occupied by an opponent unless the opponent is helpless. You can move through a square occupied by a helpless opponent without penalty. Some creatures, particularly very large ones, may present an obstacle even when helpless. In such cases, each square you move through counts as 2 squares.

Ending Your Movement

You can’t end your movement in the same square as another creature unless it is helpless.

Overrun

During your movement, you can attempt to move through a square occupied by an opponent (see Overrun).

Tumbling

A trained character can attempt to use Acrobatics to move through a square occupied by an opponent (see the Acrobatics skill).

Very Small Creature

A Fine, Diminutive, or Tiny creature can move into or through an occupied square. The creature provokes attacks of opportunity when doing so.

Square Occupied by Creature Three Sizes Larger or Smaller

Any creature can move through a square occupied by a creature three size categories larger than itself.

A big creature can move through a square occupied by a creature three size categories smaller than it is. Creatures moving through squares occupied by other creatures provoke attacks of opportunity from those creatures.

Designated Exceptions

Some creatures break the above rules. A creature that completely fills the squares it occupies cannot be moved past, even with the Acrobatics skill or similar special abilities.

The invisibility effect in this equation doesn't really matter a whole lot, we'd resolve this just the same as if ninja was visible and the drow knew he was there.

The Drow moves up to the square adjacent to the ninja and cannot proceed into the ninja's square. He must make an Acrobatics or Overrun check to enter the ninja's square, or he can end his movement right there adjacent to the ninja, or he can use the remainder of his move action to go around the ninja using the unoccupied squares adjacent to the ninja's square.

If the drow attempts to attack or overrun, then the scenario gets a little more complicated and NOW the invisibility rules come into play. Then we start -50% miss chance, perception vs. stealth checks for pinpointing the ninja's square each time the ninja moves or 5ft steps, etc.

[VoodistMonk]

As stated, the movement into that square should be prevented by the GM. Or, the GM could "demand" an Acrobatics check or CMB [Overrun] check, to pass through that square... but you still couldn't stop in that square. There ARE exceptions, such as class abilities and racial abilities, that allow multiple creatures to share a space... but without any such abilities in play, stopping in an occupied square should be prevented by the GM... even if it signals the existence of something unseen, such is life.

[Mysterious Stranger]

The rules state you cannot move through a square occupied by an opponent. You can move through a square occupied by a friendly character unless you are charging. This kind of implies the reason you cannot move through a square is the opponent actively preventing you. This is further supported by the fact you can move through a square that has a helpless opponent.

In this case I can see the GM allowing the ninja to act as a friend as long as he is not taking any hostile action. This would allow the ninja to maintain the invisibility and move out of the way as per option 1. The GM has already ruled on that so that kind of falls under rule 0.

Personally, I would say that option two would mean that the target knows the ninja is there even if the invisibility was maintained. I am not even sure if the invisibility would remain if the character blocked drow. If the ninja cast a spell that prevents the drow from mothing through the square it would break the invisibility. So, why does blocking them not break it?

[Hugo Rune]

This is only an issue because of the turn based mechanics. If one were instead to consider the simultaneous 6 seconds of activity a round represents the answer becomes obvious.

In the case of an individual walking into or through a stationary invisible opponent, the opponent would move out of the way to avoid a collision. The individual should get a perception check to detect (hear) the movement.

In the case of the two both moving then the invisible creature would stop short to avoid a collision. If their turn was first then they would move back one square, if their turn is second they would move forward one square.

[Azothath]

from a Raw perspective 'move through' is based on ally/foe designations, which being declared states can change and each has assumptions about secondary effects (like AoOs).
'Occupying a square' has similar differences but generally is a 'no'.
The game has a lot of general cases and doesn't get into corner cases often. That is why it relies on a GM to arbitrate/adjudicate these unlikely situations. The rules don't exist in a vacuum, there are at least one player and a GM involved.
If a GM simply asks the occupying creature if it will allow friendly movement through its square the situation resolves.
The second part of this scenario is conveyed information and Game Balance. It's not 'fair' that a creature learns of a tactical situation because of the granularity of RAW. Creatures cannot detect invisible creatures by finding squares they cannot move into unless the invisible creature agrees. Movement is different than searching a square.
While we use squares to define movement in RAW do the characters in the game actually know and see these tactical conceits(lines on a map)? It's tricky as spells use them for targeting.

[Kasoh]

Azothath wrote:

If a GM simply asks the occupying creature if it will allow friendly movement through its square the situation resolves.

Its not fair play to have the enemy change friend/foe designation whenever it is convenient for it. That's not how that works, otherwise you could use that to avoid attacks of opportunity, avoid having to tumble through foes and a bevy of other consequences.

[Azothath]

Kasoh wrote:

Azothath wrote:

If a GM simply asks the occupying creature if it will allow friendly movement through its square the situation resolves.

Its not fair play to have the enemy change friend/foe designation whenever it is convenient for it. That's not how that works, otherwise you could use that to avoid attacks of opportunity, avoid having to tumble through foes and a bevy of other consequences.

it is fair when the GM asks.

[Pizza Lord]

Long Explanation:

---------------------------------------------
There is no specific 'invisible creature in space you stopped in rule' so we have to use and extrapolate an answer based on the rules there are (and also what makes sense from a gameplay and common sense standpoint).

There is a rule against being able to move through an opposing creature's square (with some exceptions; overrun, size differences, etc.) There is also clear indication that you can move through a friendly square. The implication is that it's because the creature wants to allow you to pass through its square.

Just like a totally unequivocal foe can choose to let someone run right past them on an overrun, there's no reason any creature can't just let a creature pass by it (unless it fills the space, like a gelatinous cube) or they legitimately couldn't move out of the way, like they're squeezing in a narrow space or on the ladder or rope you're climbing up or down.

Invisibility wrote:

A creature can grope about to find an invisible creature. A character can make a touch attack with his hands or a weapon into two adjacent 5-foot squares using a standard action. If an invisible target is in the designated area, there is a 50% miss chance on the touch attack. If successful, the groping character deals no damage but has successfully pinpointed the invisible creature’s current location. If the invisible creature moves, its location, obviously, is once again unknown.

For game balance purposes, allowing a character to 'scan' for invisible enemies by merely passing into every 5 foot space (typically at least 6) with one move-action just to be 'magically blocked by a GM forcefield' and thereby pinpointing an invisible creature's location is not supported, especially when there are methods or abilities or talents that allow for such 'sweeping' of an area, typically requiring a standard action. Letting someone check 6 or more squares for a move action (and then getting to use their standard for attack when they hit the 'forcefield' would not make sense). Granted, the invisible creature could take an attack of opportunity, but that's besides the point here, since this would still be a benefit to an attacker or searcher over the defender (at least, defender in the case of this activity and action). The GM should give the leeway and advantage to the concealed creature and they should most definitely not just act like there's a five-foot square forcefield around an invisible creature that lights up like a pinball machine bumper going *Ka-ching!*.

Invisibility wrote:

If a character tries to attack an invisible creature whose location he has not pinpointed, have the player choose the space where the character will direct the attack. If the invisible creature is there, conduct the attack normally. If the enemy’s not there, roll the miss chance as if it were there and tell him that the character has missed, regardless of the result. That way the player doesn’t know whether the attack missed because the enemy’s not there or because you successfully rolled the miss chance.

While this details the results for an active attack into a square where an invisible target is believed to be, we can see that the rules are very on the side of keeping the invisible creature's location a secret and concealed; requiring miss checks and even going out of the way to not hint that a PC is choosing wrong by secretly rolling and keeping them in the dark. It would not mesh with these methods to just let someone with a high move speed, like a barbarian or monk just move-action and then pinpoint and attack in one round with nothing the defender can do.

Just like a character can choose to make it easy to get hit or let someone hit them (maybe barring a roll of natural 1 from the attacker at the GM's discretion) a foe can just let someone go past them and their square. If an attacker/searcher is somehow lunging or charging through a square that they highly suspect has the invisible creature (which is basically a grope, as listed above and should be limited to two spaces at most) then the defender would have to rely on the 50% miss chance as normal.

As stated, there's no direct rule, but I think this is the most fair for such situations. In the case of someone stopping in the invisible creature's space (unaware), then I'd certainly allow the evading creature a chance to move to an available space subtly (though a Perception check for movement to hear them would be called for, free movement or not), and providing that there is such an available space.

I feel this a fair ruling (not the official rule) because the 5 Foot Square method is basically for combatants who are controlling their space and can control up to a five foot area. In the case of someone who is not halting entry into their square, this should not apply. Just like 3 or 4 humans could stand together in a 5 foot square elevator and could actually brawl or have a fight in one, sometimes you have to make a common sense call. You just assume they've all allowed themselves to get up close (and the GM can make bonuses or penalties to attack or defense based on that specific situation).
--------------------------------------------------------

TL;DR
In this case, the invisible creature should fully be allowed to let a creature pass through its space, whether it's friendly or not. Just like an ally who is invisible can allow a character to pass through or suddenly say "Wait, I stop my ally from passing by when he tries to." That is a reasonable thing a person can do (and even if you say blocking would cause loss of invisibility, it probably doesn't apply since it's an ally). A person can fail saves, let someone hit them and not dodge, or not contest control or block a space (assuming they have the capacity to move out of the way).

[Mysterious Stranger]

Just because you consider someone friendly does not mean they consider you friendly. How would declaring someone friendly allow you to gain any advantage, when they still consider you an opponent? You still provoke AoO from them because you are their opponent. They don’t provoke AoO from you because they are your friend.

Changing the friendly designation happens all the time in the game. For example, if someone is pretending to by my friend and I cast a healing spell on them I don’t need to make an attack roll because they are an ally. After I heal the “friend” he stabs me in the back getting sneak attack he is not going to be considered friendly anymore.

[Ryze Kuja]

Per RAW, the Drow shouldn't be allowed to enter the Ninja's square without an Acrobatics or Overrun check. However, it is realistic to believe that an invisible creature (especially a Ninja) would be able to allow a creature to pass through their square while remaining unnoticed. Personally, I would allow this in a heartbeat. Even though it isn't per the rules, it's still not game-breaking in the slightest, nor an unrealistic request. But allowing someone to pass through your square while you remain unnoticed would certainly be difficult, so I'd require a check of some kind.

I would probably ask the Ninja do an Acrobatics check as if he were "moving through an enemy's space" and "at full speed", which would be "Drow's CMD +5" and an additional "+10" for full speed, so "Drow's CMD +15" = Acrobatics DC to avoid the Drow passing through his space at full speed. Alternatively, I would also accept a Stealth check vs. Drow's CMD +15 to allow the Drow to pass through your square at full speed and the ninja remains unnoticed. If the Drow was only moving half speed for w/e reason, then it would only be a Drow's CMD +5 DC.

Even though you can willingly allow an enemy to pass through during an Overrun check, the difficulty here is allowing the enemy to pass through your square while you remain unnoticed (without touching him, his weapon/shield, his backpack and gear, etc.). So I'd require a check. I think that's perfectly fair, tbh.

==================================================

The only thing weird about the OP's scenario is that the Drow's movement ENDS in the ninja's square and the Drow doesn't continue into an unoccupied square. So, if I were GM, I wouldn't allow the Drow to enter the ninja's square at all. Because then you'd end up with a scenario that is a clear violation of the rules where two medium creatures are occupying the same square at the end of their turns.

If the Drow is at 25ft Movement for the round and I've stopped his movement as the GM, and the Drow is still hell-bent upon entering that square to finish the last 5ft of his movement, then he can perform an Acrobatics or Overrun to move through it, and end his turn in the square on the opposite side of the Ninja. If the Drow fails this check, then he ends his turn in the square in front of the Ninja.

[Azothath]

this topic has been debated for 20+ years. Still comes down to the GM resolving the situation in his home game in some manner.
I've seen it allow PCs to discover invisible creatures, requiring the invisible creature avoid the intruder(skill check), to allowing no interaction/information.

[Claxon]

I mostly agree with Ryze Kuja, but I don't know that I'd use exactly that skill check for the Ninja, but I'd probably have some sort check for the ninja to 1) move out of the way & 2) avoid being noticed moving out of the way. And then if the enemy did want to stay in that square I would allow the ninja to spend an immediate action to move into an adjacent square (assuming no difficult terrain) and have their movement decreased by 5ft on their next turn.

[Mysterious Stranger]

The rules are an abstraction to make it easier to play the game. Sometimes those abstractions actually make it harder to play the game. Turns are part of that abstraction; they allow the combat to be broken up into discrete segments so that each character can act in a reasonable manner. The thing to keep in mind is that all the actions are actually taking place simultaneously. The drow is not suddenly moving through the ninja’s square with no warning. He is taking 6 seconds and moving at a normal pace, the ninja is aware of this and has plenty of time to step aside. Forget about the invisibility or attacks of opportunities. If someone you are aware of is 30 feet away from you and walks towards you how difficult is it to avoid them? Personally, the only time anyone has ever run into me is either when neither of us saw the other, or they were actively trying to run into me. The ninja is aware of the drow and the drow is not attempting to run into him. The idea that the character has to loses 5 feet of movement next turn is a good idea but making them make an acrobatics roll going too far.

A stealth roll to avoid being noticed would be appropriate.

[Kasoh]

Mysterious Stranger wrote:

The rules are an abstraction to make it easier to play the game. Sometimes those abstractions actually make it harder to play the game. Turns are part of that abstraction; they allow the combat to be broken up into discrete segments so that each character can act in a reasonable manner. The thing to keep in mind is that all the actions are actually taking place simultaneously. The drow is not suddenly moving through the ninja’s square with no warning. He is taking 6 seconds and moving at a normal pace, the ninja is aware of this and has plenty of time to step aside.

Or, the interpretation that these events are happening relatively simultaneously prevents the ninja from just stepping aside. The ninja is also doing something on his turn. Maybe moving, maybe readying an action, maybe nothing, but at the same time, the drow is also moving and because the drow had higher initiative, he is just a bit faster and walks into the ninja who did not react in time, because they were just a little bit slower. After all, the ninja has no way of knowing where the drow is going to stop and maybe the ninja isn't going to risk the +20 not moving bonus to invis or whatever.

[Mysterious Stranger]

A higher initiative is a game term and part of the abstraction. In the game we wait for a player to complete their turn before the next person goes. In real life that is not how things happen. When the drow starts moving towards the ninja he is not going to wait until the drow spends six seconds walking up to him to react. If the drow is taking 6 seconds to move that is more than enough time for the ninja to step aside.

Unless the ninja is blind, he can see the drow walking towards him. Noticing a visible creature is a DC 0 perception roll assuming the drow is 30 feet away that would be DC 3 roll. Unless the Ninja somehow has a 2 or less bonus on perception and rolls a 1 there is no chance, they do not see the drow walking up. Considering perception is a class skill for ninja’s and it is the most important skill in the game he should have at least a +4 even at first level. Wayang get a racial bonus to perceptions so even with a 5 WIS the minimum perception bonus for the ninja is +3 if he spent at least a single point on perception.

The fact the OP stated the GM ruled the Ninja could move as a free action is a pretty clear indication that the ninja knew that the drow was going to move through his square.

The ninja still gets a +20 bonus to stealth even if he moves. If he does not move the bonus is +40. Considering the character is small and has a racial bonus to stealth he should still have at least a +31 roll to stealth with a single point in stealth.

[Kasoh]

Mysterious Stranger wrote:

A higher initiative is a game term and part of the abstraction. In the game we wait for a player to complete their turn before the next person goes. In real life that is not how things happen. When the drow starts moving towards the ninja he is not going to wait until the drow spends six seconds walking up to him to react. If the drow is taking 6 seconds to move that is more than enough time for the ninja to step aside.

The ninja obviously has a plan they are wanting to enact as well. Sneak attacking someone from invisibility maybe. Stealing the idol, whatever. They would be doing that at the same time as the drow, not waiting to react to whatever that guy was doing. Why does the ninja get to react to the approach of the drow instead of the drow getting to run into the ninja? Both are equally feasible if everyone is acting at the same time.

If only there was some way of determining who had a faster reaction time, we could use that to determine whose actions take precedence...

[VoodistMonk]

If only there was a way...

[Azothath]

Resolving multiple creatures in a square - Homebrew forum thread