D&D 5E Problems with Illusions

[jaelis]

My read is that they can make the Int check to render the illusion transparent. Evidently that involves some kind of detailed study. But that doesn't mean the Int check is required to realize the illusion is an illusion, that can happen automatically with some kind of interaction.

 

[Kobold Stew]

Seeing through illusions is weird.

Above, I suggested an automatic Int (Arcana check) to recognize the illusion; there may be a better option, though.

What about allowing a passive Int (Investigation) check? Because it uses the passive number, the DM doesn't alert the party that a check is being made, but anyone who has a passive investigation high enough just automatically sees through the illusion?

That doesn't require a turn for investigation, and puts a (limited) use on a check that otherwise has very little purpose in the game (but does get called out in the Observant feat).

 

[jaelis]

What about allowing a passive Int (Investigation) check? Because it uses the passive number, the DM doesn't alert the party that a check is being made, but anyone who has a passive investigation high enough just automatically sees through the illusion?

IMO that would unduly nerf illusions, but if it works at your table, go for it

 

[Ovinomancer]

The investigation check isn't a 'squint at it', it's like examining a scene in a movie to spot the CGI. The DC of the spell represents how well the illusion mimics the real world and the investigation check is taking a moment to look closely (without touching) and pick out the artifacts. A success means you've identified something that shows the illusion isn't real (shadows going the wrong way for the lighting, the wall actually floats a half inch off the ground, etc) and a failure means that you can't tell it's not [-]butter[/-] real. You're looking for the points where it fails to mimic reality well enough.

As for illusions going transparent, I've houseruled that out. Illusions never go transparent -- they either exist and everyone sees them (but may recognize they're not real) or they don't exist. This prevents the one-way visible walls. Illusory Walls block line of sight for everyone, even the caster. Seems to remove a lot of the wonkiness with using illusions and tracking who can see through them and who can't. Now I just have to track who believes them to be real, and that's easier for me to do.

 

[Kobold Stew]

The investigation check isn't a 'squint at it', it's like examining a scene in a movie to spot the CGI.

I find this interesting. It's looking at it in real time, for a handful of seconds. I'm not sure there's any real difference in play, but I'll admit your description is much tighter.

As for illusions going transparent, I've houseruled that out. Illusions never go transparent -- they either exist and everyone sees them (but may recognize they're not real) or they don't exist.

Thanks. What happens with repeat castings? When a disbelieved illusion is superposed does that require another check? Should it? Should it have advantage (since the viewer has already disbelieved something similar) or disadvantage (since the new illusion makes the viewer doubt what they saw was in fact there)?

 

[Kobold Stew]

IMO that would unduly nerf illusions, but if it works at your table, go for it

Would it? I'm not sure. Assume a 16 Int wizard casting illusions at level 1 -- the passive investigation of anyone not trained in spotting inconsistencies (investigation) is never going to match that unless the intelligence of the opponent is also 16. How frequent is that?

Or do you mean it nerf it for NPCs? It does (since PCs are trained in many more skills), but it then circumvents much of the wonkiness in the OP.

I'm looking for solutions!

 

[Ovinomancer]

I find this interesting. It's looking at it in real time, for a handful of seconds. I'm not sure there's any real difference in play, but I'll admit your description is much tighter.

Thanks. What happens with repeat castings? When a disbelieved illusion is superposed does that require another check? Should it? Should it have advantage (since the viewer has already disbelieved something similar) or disadvantage (since the new illusion makes the viewer doubt what they saw was in fact there)?

The illusions were tralking about are concentration, yes? I'm afb, but I recall they mostly are, so that limits super-imposition. If you have two casters trying to cover failed illusions, that's going to look wonky to those that haven't identified the illusions. I might even allow automatic detection for two illusions of the same thing trying to exist at the same time in the same place.

If a caster drops an illusion and trys the same thing again, I'd allow anyone who had already detected the illusion to assume the second is also an illusion without a check necessary. Of course, if it's not an illusion the second time, that's when it gets fun. A best use of illusion I've seen was to cast a poor illusion of an approaching monster that the caster knew was actually on the way and have the illusion do unbelievable things. All the bad guys recognized it as an illusion, and then, when the real thing showed up a moment later, believed out was illusory as well. Hijinks ensued.

 

[jaelis]

Would it? I'm not sure. Assume a 16 Int wizard casting illusions at level 1 -- the passive investigation of anyone not trained in spotting inconsistencies (investigation) is never going to match that unless the intelligence of the opponent is also 16. How frequent is that?

Or do you mean it nerf it for NPCs? It does (since PCs are trained in many more skills), but it then circumvents much of the wonkiness in the OP.

I'm looking for solutions!

From the player's point of view, you're saying you'd start with a DC 15, so only an Int 20 untrained NPC would notice? I agree, that probably just won't do much at all. But then, why bother?

Against the PC's it would be another story, and I guess I like the idea of having to test for illusions better than having one high-Int character with Invest. proficiency be able to see through them mostly.

TBH though I don't totally understand the problem you're trying to solve, so I'm probably not being very helpful. The things you listed in the OP seem relatively straightforward to me, so we're probably just on a different wavelength.

 

[Kobold Stew]

The illusions were tralking about are concentration, yes?

Minor image is not concentration, and lasts 10 turns.

 

[Kobold Stew]

From the player's point of view, you're saying you'd start with a DC 15, so only an Int 20 untrained NPC would notice? I agree, that probably just won't do much at all. But then, why bother?

Not sure where DC 15 came from. I assume a level 1 wizard 16 Int has DC 13; Anyone with 16 Int would have a default passive Investigation of 13.

I don't know how to explain the why bother clearer than I have. I do appreciate your answers.