Wall of force creates an invisible wall, and that leads me to ask some questions about how that works.
1. Is the wall undetected due to the invisible condition?
2. If no one successfully identifies the spell, is the wall unnoticed?
3. Does targeting the wall require a DC 11 flat check? The phrase "missing the broad side of a barn" comes to mind.
4. If someone tries targeting an enemy on the other side of an unnoticed wall, does the wall get targeted instead?
5. If someone tries placing an area effect (like a fireball) on the other side of an unnoticed wall, does the origin point appear on the near side instead?
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1. Yes. Including the AoN link it to the invisible condition.
2. Yes but not exactly doesn't notice it. Those who saw the spell being cast will know that some spell was cast without knowing its effect, yet this creature still can Seek to find something unusual and notice the wall with the GM having to judge the DC (probably using the spell DC).
3. It's a good question. RAW yes, but RAI, I doubt that is the intention. Maybe some GM may interpret that once you don't see the exact angle of the wall, your attack may fail in a similar way that it fails against an invisible creature or object. Yet this doesn't sound reasonable; it makes more sense if someone is trying to attack the wall, it won't need to do a flat check because the wall is much too large and plain to miss it more than a normal AC 10 check would.
4. RAW no. The attack just fails due to the lack of Line of Effect. RAI may be reasonable enough to hit the wall instead.
5. RAW the spell fails due to the lack of Line of Effect. RAI it still reasonable that a fireball exploded in contact with the wall.
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In general these cases aren't covered by the rules, so they are subject to GM fiat. Most interactions with objects fall into these undefined situations because we lack from clear rules about how many things interacts with objects (by RAW you cannot Strike objects for example even with many things in the game expecting that you can do).
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I think the entry for walls would be far too long if you had to cover every single possible ruling. GMs have to do their best with it.
From my perspective, it's still a wall. There is no missing it as long as you are striking where it is. It is a defensive wall so usually cast to protect something on the other side of it. It has an AC, hardness, and hit points, so it lasts as long as the hit points remain. If you're striking at something on the other side of it, you hit the wall doing damage to it if you exceed its hardness.
Just like you'd see in a movie with some kind of thick glass that someone is trying to batter or blast through. They're hitting the invisible "glass" wall first trying to shatter it to get to what's on the other side.
That's generally how I play a wall of force, thus my rulings that aren't explicitly covered align with that visual.
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Now that I think about it, I suppose it would be annoying for a wizard to try to cast phantasmal calamity on all the enemies only to be told that it actually hit all the player characters instead because an invisible wall was in the way. That's not just no-selling the spell, it's turning it against the caster with no save.
If an invisible wall being in the way merely no-sells the burst placement, that's still plenty strong.
1. Is the wall undetected due to the invisible condition?
I'd never actually thought of the wall being completely invisible - just clear and transparent like a thin pane of glass or cellophane.
But yeah. It does say invisible. So it would not be against RAW to run it as actually invisible.
It might be annoying for your own party at that point though...
2. If no one successfully identifies the spell, is the wall unnoticed?
Either unnoticed or undetected. I'm not sure what the difference would be for an inanimate object. Those conditions are usually for creatures.
3. Does targeting the wall require a DC 11 flat check? The phrase "missing the broad side of a barn" comes to mind.
Targeting objects with things that don't specifically say that they target objects is something that has to be ruled on by the GM for each scenario.
Yes, "can't hit the broad side of a barn" is one extreme. But Strike doesn't target objects, nor do most spells. The rules explicitly say that damage to objects from AoE spells is up to GM discretion.
4. If someone tries targeting an enemy on the other side of an unnoticed wall, does the wall get targeted instead?
It wouldn't get targeted directly, no. Trying to cast Daze on a target on the opposite side of a wall of force probably wouldn't work because of line of effect. But it wouldn't attempt to Daze the wall itself.
5. If someone tries placing an area effect (like a fireball) on the other side of an unnoticed wall, does the origin point appear on the near side instead?
I've discussed this before. I am in the minority opinion on this. But I'll present the argument anyway. I still haven't found anyone who can successfully refute it (no, having a different opinion and conclusion doesn't refute the validity of the argument no matter how many people also agree with you).
One:
Line of Effect states:
When creating an effect, you usually need an unblocked path to the target of a spell, the origin point of an effect's area, or the place where you create something with a spell or other ability.
and
In an area effect, creatures or targets must have line of effect to the point of origin to be affected.
Two:
Different effects can have different line of effect types, especially when dealing with Wall spells. For example, an arrow fired from a bow will not have unblocked line of effect to the target on the opposite side of a Wall of Wind. However, Daze would not be affected by Wall of Wind at all--both targeting and the spell's effect could pass through the wall with no obstruction.
Three:
Spell Ranges, Areas, and Targets states the following:
Some spells allow you to target a creature, an object, or something more specific. The target must be within the spell's range, and you must be able to see it (or otherwise perceive it with a precise sense) to target it.
and
A spell that has an area but no targets listed usually affects all creatures in the area indiscriminately.
Analysis:
Fireball has two different "line of effect" calculations that need to be made.
* The first is between the caster and the point of origin of the burst area.
* The other is between the origin point of the burst area and each creature inside the burst radius who would be within the area defined.
Fireball also does not specify what effect type is needed for each of these line of effect calculations.
The rule for Targeting does specify that the type of effect needed for targeting "a creature, an object, or something more specific" is a vision (or other precise sense) type of effect. I maintain that the origin point of a burst area on the ground falls into the category of "something more specific" and would fall under this rule. If targeting the origin point of a burst does not fall under this rule, I challenge anyone who claims otherwise to list what other rule would specify the type of effect better.
So my conclusion is that a spellcaster only needs a visual line of effect (often called "line of sight") to the opposite side of the wall of force in order to target the origin point of the burst successfully. They need line of effect for the fire damage only between the origin point of the burst and each target within the area of effect.
Yeah, line of sight is just line of effect plus you can precisely sense the target.
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Yes, that’s why I mentioned in my post that, based on RAI, a GM might reasonably rule that a fireball explodes upon contact with a wall of force; however, under RAW, the spell simply fails to function due to the lack of Line of Effect.
That said, as others have rightly pointed out, relying on RAI—while it might prevent wasting a spell—can also lead to unexpected side effects with other AoE spells, such as unintended friendly fire. This illustrates how using RAI in PF2e introduces significant uncertainty and can produce highly unpredictable results. Consequently, sticking to RAW as strictly as possible—even when it seems absurd in certain situations—at least provides a solid sense of "rules stability" for the game.
There can be some corner cases for casting a spell across a Wall of Force. If the wall does not go all the way to the ceiling, then there could still be line of effect for some spells. there are no barriers to block the travel of the magical energy to a spot if it goes through the gap.
Another spell type are those that could go around the WoF instead of through. Most teleportation effects should be able to travel around the WoF unless it has a very short range (5ft).
WoF does not stop sound or light, so some spells with the auditory or visual traits may still work.
First, "When creating an effect, you usually need an unblocked path to the target of a spell, the origin point of an effect's area, or the place where you create something with a spell or other ability."
That is the part you're incorrect about. You are creating an effect with an area with the fireball spell, a burst effect with an origin point. So that first line applies
We might disagree on that. But that does not prove that I am incorrect.
A visual line of effect is still a line of effect. So the first line applies and is required, but is also satisfied.
>So my conclusion is that a spellcaster only needs a visual line of effect (often called "line of sight") to the opposite side of the wall of force in order to target the origin point of the burst successfully. They need line of effect for the fire damage only between the origin point of the burst and each target within the area of effect.
It's not "often called" Line of Sight. Line of Sight is its own rule defined in its own named section on p.427 of PC1 after Line of Effect on the page before.
The two are defined in (very slightly) different places in the book. But they are defined to be mechanically identical. Right down to the 1-foot square gap rule and the example of a portcullis.
As far as I can tell, listing the general line of effect rule and following it with a separate line of sight rule specifically for vision effects is done for historical reasons - so that people familiar with previous TTRPG games who go looking for line of sight rules will find it successfully.
So, second challenge (and don't think I haven't noticed that no one has attempted the first challenge yet): Define a mechanically significant difference between a visual line of effect and line of sight.
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Alternatively, how about a proof by contradiction.
Let's assume for the moment (because that is how proof by contradiction works) that line of effect and line of sight are two distinct and separate game mechanics. Which leads to the conclusion that the caster casting Fireball needs line of effect to the origin point of the burst, but not line of sight. Therefore the invisible but physically obstructing Wall of Force blocks that line of effect and prevents the spell even though it does not block line of sight.
Now we have a problem with a different wall spell: Wall of Shadow.
Fireball only requires line of effect between the caster and the origin point of the burst. Wall of Shadow does not block that line of effect since it is not a physical barrier. So now the caster can successfully target a point on the opposite side of the wall even though they cannot see it.
Being able to target an area spell to a location that the caster cannot see is a violation of the rules for Targeting.
Which concludes the proof by contradiction. Assuming that your interpretation is correct, we logically come to a contradiction in the rules. Therefore your interpretation of the rules is not correct and visual line of effect and line of sight are the same mechanical concept.
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Yeah, we can quibble about whether the fireball would appear on the near side or not at all. But there's no question that you need line of effect to the origin point, and a total obstruction would prevent line of effect even if you can see through it.
Also, the wall does explicitly allow teleportation and visual effects to pass through.
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Let's assume for the moment (because that is how proof by contradiction works) that line of effect and line of sight are two distinct and separate game mechanics. Which leads to the conclusion that the caster casting Fireball needs line of effect to the origin point of the burst, but not line of sight. Therefore the invisible but physically obstructing Wall of Force blocks that line of effect and prevents the spell even though it does not block line of sight.
Now we have a problem with a different wall spell: Wall of Shadow.
Fireball only requires line of effect between the caster and the origin point of the burst. Wall of Shadow does not block that line of effect since it is not a physical barrier. So now the caster can successfully target a point on the opposite side of the wall even though they cannot see it.
Being able to target an area spell to a location that the caster cannot see is a violation of the rules for Targeting.
Which concludes the proof by contradiction. Assuming that your interpretation is correct, we logically come to a contradiction in the rules. Therefore your interpretation of the rules is not correct and visual line of effect and line of sight are the same mechanical concept.
Where are you getting “you can’t target a square you can’t see” from. I don’t see anything about that in the targeting rules.
There are some spells that require line of sight in addition to line of effect (i.e. magic missile) but fireball doesn’t say anything about that. You simply designate a point. I see no reason that couldn’t be “20 feet in front of me past the wall of shadow”. It’s an area effect.
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Fireball only requires line of effect between the caster and the origin point of the burst. Wall of Shadow does not block that line of effect since it is not a physical barrier. So now the caster can successfully target a point on the opposite side of the wall even though they cannot see it.
Being able to target an area spell to a location that the caster cannot see is a violation of the rules for Targeting.
This is incorrect since Fireball (and other Area effects) do not Target anything, as evidenced by the fact they don't have a Target line. Nor do the Area rules ever refer to targeting or seeing.
Note, also, how the Line of Effect subsection in Effects (which you even quoted previously) says:
"When creating an effect, you usually need an unblocked path to the target of a spell, the origin point of an effect's area, or the place where you create something with a spell or other ability."
Meaning an effect's target (for example, the bandit we want to hit force barrage), the origin point for an area effect (our fireball center) and "places" (for example, the square an Eidolon appears in when we use Manifest Eidolon) are all different things.
fireball and other burst area effects do have two lines of effect: one from the caster to the center of the burst, and one from the center of the burst to all the creatures the spell can affect. wall of force prevents both, so you can't put a fireball behind it, unless you're flying or on higher elevation and can draw line of effect over the wall's 20 foot height. And if you did manage to do it, anyone on the opposite side of the wall would be safe from the fireball (or whichever burst effect you put down).
The two are defined in (very slightly) different places in the book. But they are defined to be mechanically identical. Right down to the 1-foot square gap rule and the example of a portcullis.
As far as I can tell, listing the general line of effect rule and following it with a separate line of sight rule specifically for vision effects is done for historical reasons - so that people familiar with previous TTRPG games who go looking for line of sight rules will find it successfully.
The two are actually defined in the same place, Page 426 of Player Core. And they're two different things, since, after all:
Visibility doesn't matter for line of effect.
But it very much matters for Line of Sight, which leads us to:
So, second challenge (and don't think I haven't noticed that no one has attempted the first challenge yet): Define a mechanically significant difference between a visual line of effect and line of sight.
This challenge fails because there's no such thing as a visual line of effect, as established right above where visibility doesn't matter. You're confusing the fact that choosing Targets requires that you have Line of Sight to them with what Line of Effect is.
TL;DR: If an Effect has a Target, it requires both Line of Sight and Line of Effect. If an Effect doesn't have a Target, it still requires Line of Effect. The origin point for Areas are not Targets, and so they only require Line of Effect, not Line of Sight.
Some effects, like the clairvoyance and clairaudience spells ignore these rules, but the general rules are clear as day.
Actually, Force Barrage requires you to see the target because it says so.
The general rule for spells with a Targets entry is that your GM decides whether you can target a creature you can't precisely sense. If they do allow it, you have to deal with the usual flat checks and square guessing that come with targeting creatures you can't see.
Wish there was guidance on when to allow or not allow it, though. FAQ CANDIDATE, perhaps?
Actually, Force Barrage requires you to see the target because it says so.
The general rule for spells with a Targets entry is that your GM decides whether you can target a creature you can't precisely sense. If they do allow it, you have to deal with the usual flat checks and square guessing that come with targeting creatures you can't see.
Wish there was guidance on when to allow or not allow it, though. FAQ CANDIDATE, perhaps?
Probably a FAQ candidate, but even if the spell didn't have that line force barrage would require you see the target because it says "Targets 1 creature" and in Ranges, Areas and Targets it says:
"The target must be within the spell's range, and you must be able to see it (or otherwise perceive it with a precise sense) to target it"
As you point out, allowing anything else is GM discretion. The RAW is that if a spell has a Targets entry, it requires perceiving them with a precise sense, and it also requires Line of Effect unless otherwise noted.
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Fireball only requires line of effect between the caster and the origin point of the burst. Wall of Shadow does not block that line of effect since it is not a physical barrier. So now the caster can successfully target a point on the opposite side of the wall even though they cannot see it.
Being able to target an area spell to a location that the caster cannot see is a violation of the rules for Targeting.
This is incorrect since Fireball (and other Area effects) do not Target anything, as evidenced by the fact they don't have a Target line. Nor do the Area rules ever refer to targeting or seeing.
Note, also, how the Line of Effect subsection in Effects (which you even quoted previously) says:
"When creating an effect, you usually need an unblocked path to the target of a spell, the origin point of an effect's area, or the place where you create something with a spell or other ability."
Meaning an effect's target (for example, the bandit we want to hit force barrage), the origin point for an area effect (our fireball center) and "places" (for example, the square an Eidolon appears in when we use Manifest Eidolon) are all different things.
fireball and other burst area effects do have two lines of effect: one from the caster to the center of the burst, and one from the center of the burst to all the creatures the spell can affect. wall of force prevents both, so you can't put a fireball behind it, unless you're flying or on higher elevation and can draw line of effect over the wall's 20 foot height. And if you did manage to do it, anyone on the opposite side of the wall would be safe from the fireball (or whichever burst effect you put down).
The two are defined in (very slightly) different places in the book. But they are defined to be mechanically identical. Right down to the 1-foot square gap...
There is actually an interesting case involving a blinded character casting fireball, even without a clear line of sight.
Since the Line of Effect rule specifies that "Visibility doesn't matter for line of effect" if the character possesses at least one imprecise sense capable of pinpointing the targets' squares, they can choose a point among them—where they believe there are no barriers—to cast an AoE effect. This is, in fact, one of the ways spellcasters and kineticists can hit enemies while blinded.
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Actually, Force Barrage requires you to see the target because it says so.
The general rule for spells with a Targets entry is that your GM decides whether you can target a creature you can't precisely sense. If they do allow it, you have to deal with the usual flat checks and square guessing that come with targeting creatures you can't see.
Wish there was guidance on when to allow or not allow it, though. FAQ CANDIDATE, perhaps?
Probably a FAQ candidate, but even if the spell didn't have that line force barrage would require you see the target because it says "Targets 1 creature" and in Ranges, Areas and Targets it says:
"The target must be within the spell's range, and you must be able to see it (or otherwise perceive it with a precise sense) to target it"
As you point out, allowing anything else is GM discretion. The RAW is that if a spell has a Targets entry, it requires perceiving them with a precise sense, and it also requires Line of Effect unless otherwise noted.
Just to be clear, the GM discretion I speak of is RAW.
"The target must be within the spell's range, and you must be able to see it (or otherwise perceive it with a precise sense) to target it. At the GM's discretion, you can attempt to target a creature you can't see, as described in Detecting Creatures on page 434. If you fail to target a particular creature, this doesn't change how the spell affects any other targets the spell has."
That's why the line in force barrage matters. Even if your GM usually allows a flat check to target unseen creatures with spells, that discretion doesn't apply to force barrage, because the spell itself also requires you to see the target.
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Actually, Force Barrage requires you to see the target because it says so.
The general rule for spells with a Targets entry is that your GM decides whether you can target a creature you can't precisely sense. If they do allow it, you have to deal with the usual flat checks and square guessing that come with targeting creatures you can't see.
Wish there was guidance on when to allow or not allow it, though. FAQ CANDIDATE, perhaps?
Probably a FAQ candidate, but even if the spell didn't have that line force barrage would require you see the target because it says "Targets 1 creature" and in Ranges, Areas and Targets it says:
"The target must be within the spell's range, and you must be able to see it (or otherwise perceive it with a precise sense) to target it"
As you point out, allowing anything else is GM discretion. The RAW is that if a spell has a Targets entry, it requires perceiving them with a precise sense, and it also requires Line of Effect unless otherwise noted.
Just to be clear, the GM discretion I speak of is RAW.
"The target must be within the spell's range, and you must be able to see it (or otherwise perceive it with a precise sense) to target it. At the GM's discretion, you can attempt to target a creature you can't see, as described in Detecting Creatures on page 434. If you fail to target a particular creature, this doesn't change how the spell affects any other targets the spell has."
That's why the line in force barrage matters. Even if your GM usually allows a flat check to target unseen creatures with spells, that discretion doesn't apply to force barrage, because the spell itself also requires you to see the target.
If a GM decides to allow targeting a creature by disregarding the"you must be able to see it" of the general case, I do not see how they will not allow the same for the specific spell.