D&D 4E Seeing through Illusions in 4e

[Altamir]

I ran into a little snag while developing a short one off adventure to run my group through, to test run 4e. I wanted to use an illusionary wall or landscape in my dungeon. However, I couldn't really come up with a system for how the players would be able to see through the illusion. My first though was that it would be against their Will Defense, but it didn't really make sense to me. The illusion shouldn't roll against them, since it isn't directly interacting with them, its just sitting there. I thought perhaps a straight perception check would be best, but it didn't really have anything to do with the magical nature of it. I thought that a trained Arcana check might work, but wouldn't really cover it. Would they need to make a straight Intelligence or Wisdom check against it? and if so what would it be against? I would think that every class would need at least a decent chance to see through an illusion.

So I put it to you guys, how do you think its handled officially in 4e? Obviously any illusion cast while the PCs can see it, or directly interacting with the PCs would be against their Will Def. But what would be needed to be rolled to notice an illusion already in place long before the party ever encounters it? I'm pretty sure its something obvious, and that my mind is still thinking very much 3.5ish. Your thoughts and opinions on this are greatly appreciated. Thanks in advance.

 

[Njall]

Uhm, a basic attack roll, depending on the power of the illusion itself, against passive perception scores? Then, if they notice something unusual, you set different DCs and resolve the whole thing with Search/Arcane knowledge/an active perception roll, depending on what the pcs come up with.
Just my opinion, YMMV.

 

[Benimoto]

I think it's just as simple as their passive perception score. If it's too low, they get suckered in. If they get suspicious make an active perception check then they can use that.

So yeah, my opinion is passive perception=initial save. It's even better since you don't have to ask them to roll. Active perception check=I disbelieve.

 

[mach1.9pants]

I think it's just as simple as their passive perception score. If it's too low, they get suckered in. If they get suspicious make an active perception check then they can use that.

So yeah, my opinion is passive perception=initial save. It's even better since you don't have to ask them to roll. Active perception check=I disbelieve.

This. passive just for seeing the illusion, active perception check if they are suspicious or physically interact with the illusion

 

[Finist The Falcon]

I have a feeling that when the books actually come out, they will have you role against the player's Will defense values.

While the wall may not move, the magic that created the wall is trying to infiltate the minds of those looking at it, trying to make them see something that isn't there.

 

[dm4hire]

Actually I agree with it being a passive insight or passive perception check to detect something out of the ordinary or perhaps an insight/perception check against the DC of the illusion. Illusions are the domain of the illusionist not covered in the PHB so most likely will have set DCs for stuff like illusionary wall and such.

 

[VBMEW-01]

I have a feeling that when the books actually come out, they will have you role against the player's Will defense values.

While the wall may not move, the magic that created the wall is trying to infiltate the minds of those looking at it, trying to make them see something that isn't there.

I agree with this as maybe a 1/2 Caster Level+Ability Modifier v/s Willpower as the initial test. Afterwards, you could use passive perception if they have reason to disbelieve. Additionally, Insight could let them earn a Perception check, to say they stumbled on it.

I really do wonder how these will be handled.

 

[Altamir]

Thanks for all the great ideas guys. This was just one of those things where the more I sat and thought about it the more I thought .. "Hrm, How the heck are they going to do this?" I think for now I'm going to go with the passive perception to see if they notice anything weird (The light not creating the correct shadows, etc.) followed by are more active check against their will defences if they interact with it.

 

[ZappoHisbane]

Whether we use Perception or Will Defence will depend on the type of Illusion. To use 3.5 terms, if it's a Figment or Glamer then you'd need to use Perception to notice that it's an illusion since it's something that is interacting with you via your senses. Phantasms on the other hand are mind-affecting, and thus a roll against the PC's Will Defense would be appropriate. Patterns (as described in the SRD) affect both the senses and the mind, so some combination of the two would be appropriate.

To sum up, if the illusion is something that is consistant to all parties involved and can be seen, heard, touched, smelt or tasted, Perception is probably what you'll want to use. If the Illusion is 'all in your head', and (possibly) varies from victim to victim, that would be against the Will Defense. Seems pretty straightforward to me.

Edit: As an aside, I've always thought that the strictly mind-affecting illusions (like Phantasmal Killer, though it's doubtful that spell has survived in 4e) should be under the Enchantment school. Playing with light and shadow, sound and silence, that's Illusion. Playing tricks on somebody's mind? Enchantment.

 

[Iron Sky]

I would think it would be insight vs illusions rather than perception since the point of an illusion is to decieve your senses...

"Perception - use this skill to notice clues, spot imminent dangers, and locate hidden objects."

"Insight - Use this skill to discern intent and decipher body language, making a best gues as to a target's motives, attitudes, and truthfulness."

More likely, I'd just do an attack against Will of some sort since illusion generally required will saves in 3.x.