Can an illusion of a wall grant concealment?

Question

Imagine a scenario in which the PCs' enemies are 50 feet away. A level 3 wizard thinks it's a great idea to divide the groups and casts the spell silent image and, with it, create an illusory stone wall.

If I am reading the text correctly he can create the illusion of a stone wall that's 10 feet thick, 10 feet high and 70 feet long.

Assuming all participants fail their Will saving throws, does this illusory stone wall grant both groups total concealment?

If the wizard decides instead to create the illusion of a one-way mirror with the same dimensions would that grant only the PCs total concealment?

Answer 1

Yes

But those who interact with it are allowed a Will Save. So if you cast right in front of your allies, you can tell them that it's an illusion and they can touch it and gain a will save, those 50 feet away are not allowed a will save until they interact with the illusion in some way, such as shooting an arrow at it.

Silent Image is a figment:

Figment: A figment spell creates a false sensation. Those who perceive the figment perceive the same thing, not their own slightly different versions of the figment. It is not a personalized mental impression. Figments cannot make something seem to be something else. A figment that includes audible effects cannot duplicate intelligible speech unless the spell description specifically says it can. If intelligible speech is possible, it must be in a language you can speak. If you try to duplicate a language you cannot speak, the figment produces gibberish. Likewise, you cannot make a visual copy of something unless you know what it looks like (or copy another sense exactly unless you have experienced it).

Because figments and glamers are unreal, they cannot produce real effects the way that other types of illusions can. Figments and glamers cannot cause damage to objects or creatures, support weight, provide nutrition, or provide protection from the elements. Consequently, these spells are useful for confounding foes, but useless for attacking them directly.

Also, the spell says it does not create texture, so if they touch the wall with their bare hands, they will most likely automatically know it's not real (no will save required) and can walk right through the illusion, but will not see it as a translucent image unless they pass their save.

The illusion does not create sound, smell, texture, or temperature.

If someone (ie: the caster) tells them that it's an illusion, they gain a +4 bonus to their will saves:

If any viewer successfully disbelieves an illusion and communicates this fact to others, each such viewer gains a saving throw with a +4 bonus.

The thing is, if wether you know it's an illusion or not does not automatically make your brain believe it. That's the point of illusions, tricking the senses. Though i do agree that it's the magic school that sees the most table variation in the game. Even if you know it's a silent image, like identifying it as it's being cast, someone told you what it is and what it does, the image is there and looking very real to you. Knowing what the spell does will allow you to walk right through without analyzing it, but it does look like a real wall to your character.

What counts as interaction is normally up to your GM, as the rules do not clarify that, but that will depend on what is the illusion and how people could interact with a real version of that illusion. The Ultimate Intrigue defines this interaction as spending at least one move or standard action with the illusion, but whether or not your table uses that rule is the GM's decision.

What is interacting with a wall? Touching it, trying to climb it, hitting it with a hammer, shooting something at it, etc.

What is not interacting with a wall: Looking at it, talking to it, waving at it, yelling at it, etc. Note that some of those examples could work against other types of illusions, such as an illusory dog or bear, and would probably allow a will save, but not against an illusory wall.

Answer 2

I answer both your questions below:

Your first question:

If I am reading the text correctly he can create the illusion of a stone wall that's 10 feet thick, 10 feet high and 70 feet long.

Assuming all participants fail their Willpower saving throws, does this illusory stone wall grant both groups total concealment?

My answer: yes

The description of the spells, which is an Illusion (figment), says:

This spell creates the visual illusion of an object, creature, or force, as visualized by you. The illusion does not create sound, smell, texture, or temperature. You can move the image within the limits of the size of the effect.

The SRD also has the following to say:

Saving Throws and Illusions (Disbelief)

Creatures encountering an illusion usually do not receive saving throws to recognize it as illusory until they study it carefully or interact with it in some fashion.

A successful saving throw against an illusion reveals it to be false, but a figment or phantasm remains as a translucent outline.

A failed saving throw indicates that a character fails to notice something is amiss. a character faced with proof that an illusion isn't real needs no saving throw. If any viewer successfully disbelieves an illusion and communicates this fact to others, each such viewer gains a saving throw with a +4 bonus.

So the answer is yes it provides total concealment for anyone failing their save: they cannot see through the wall. The illusion has no "facing" it appears as the object from all directions.

The caster has absolute proof it isn't real (they cast it) and so needs no saving throw. The rest do not receive saving throws until given a good reason to think it is not real or study it closely. Their sight tells them the caster has conjured a wall.

Some thoughts on this for the DM (who is always, has to be, the final arbiter on all of this, at least once the group has agreed the base understanding):

• The caster's party might have good reason to disbelieve if it is a common tactic of theirs, but this still requires a save, perhaps at +4.
• Someone recognising the spell cast as an illusion from a high arcana skill roll would have good reason. Just the fact it magically appeared out of nowhere is not reason enough, that's what magic does.
• Arrows flying or a fighter charging through the wall, for instance, may well give everyone reason to disbelieve even though their interaction with the illusion is due to someone else's actions.
• Even being given reason to believe that the wall is an illusion only grants a save. If the save fails then the character still sees it. They need "proof" it is not real to not require a save. What constitutes proof is up to the DM as, for instance, someone with no arcana skill may not have the knowledge to have it easily proved until they have their arm pushed through it.
• Re-saves should only be allowed (in my opinion) when something significantly new occurs. If an arrow flying through triggers a failed save then more arrows won't allow another save as arrows passing through has become a "real" characteristic of the wall for the character. However someone then running through the wall would be new and would trigger a save. It is up to the DM to judge when a new save is triggered.

And lastly even those who save see the wall "as a translucent outline" as it is a figment, though this will not provide any concealment.

Your second question:

If the wizard decides instead to create the illusion of a one-way mirror with the same dimensions would that grant only the PCs total concealment?

The srd says the following about figments:

Figment: A figment spell creates a false sensation. Those who perceive the figment perceive the same thing, not their own slightly different versions of the figment. It is not a personalized mental impression. Figments cannot make something seem to be something else. A figment that includes audible effects cannot duplicate intelligible speech unless the spell description specifically says it can. If intelligible speech is possible, it must be in a language you can speak. If you try to duplicate a language you cannot speak, the figment produces gibberish. Likewise, you cannot make a visual copy of something unless you know what it looks like (or copy another sense exactly unless you have experienced it).

The key points here is "you cannot make a visual copy of something unless you know what it looks like", though you may be surprised where this leads us in ascertaining if you can make an illusion of a one-way mirror.

The illusion is not a mirror, it is a copy of a mirror showing what the caster thinks it should. A mirror would only work, only show a true depiction of the reflection, if the caster has a clear view of what is happening so as to be able to change the illusion to match the scene.

The see through side needs thought as, still, it is NOT a mirror, it is a copy of a mirror. The see though side will only show what the caster thinks it should. The caster would therefore need a clear view of the scene on the other side. Of course they automatically succeed on the save as they have proof it is an illusion so they can see right through it and can satisfy this requirement, if the lighting is good which it would need to be for any of this to work.

So my answer: yes

...if the lighting is good enough for any of it to work. However it is a complex illusion and I would suggest that the opportunities for disbelief triggering a save would be many as, for instance, watching yourself dancing around in front of the "mirror" pulling silly faces might well be deemed "close examination".

Answer 3

Yes, an illusion of a wall grants total concealment against anyone who has not saved against the illusion.

The illusion rules say: "If any viewer successfully disbelieves an illusion and communicates this fact to others, each such viewer gains a saving throw with a +4 bonus." The caster can tell their allies "this wall is illusionary", which will give them that saving throw. It's up to the DM to decide when the enemies receive saving throws, but if people start making attacks through the wall, that will presumably give it away pretty fast.

There is not, in the real world, any such thing as a one-way mirror. The things we call one-way mirrors are actually partially reflective mirrors which appear to be one-way if one side is more brightly lit than the other. If the lighting conditions on the battlefield are very favorable (the enemies are brightly lit and the allies are not), the illusionist could create an illusion of a partially reflective mirror and get that one-way effect; otherwise, attempts to create a one-way mirror will fall afoul of the rule that an illusion looks the same to everyone. ("Those who perceive the figment perceive the same thing, not their own slightly different versions of the figment. It is not a personalized mental impression.")