Using illusions, initiative, metagaming.

[Epinephrine]

How, as a DM, do you use illusions versus your PCs? Inevitably there will be party members who have spellcraft, and will recognise illusion spells as they are cast. Isn't this a HUGE weakness? If illusions are so easy to recognise when cast, how do you use them?

For example, if I wanted to imprison an attacker in a wall of stone, I could surround him with an illusionary wall of stone. If it's an illusion that affects sound as well as vision, would an illusionary wall of stone thus muffle sound as well as a real one (just as an illusionary wall blocks vision as well as a real one)?
The player thus imprisoned wouldn't be able to hear the player on the other side yell that it's only an illusion, and could easily spend his round chopping futilely at it (getting a save for interacting with it).

On a similar note - if an enemy has an illusion of fog filling a room (and is in there), and the party open the door, how do you resolve it? Initially neither side was aware of the other, so no surprise round, right? So an initiative roll is called for, but if I ask for an initiative roll it opens the door to metagaming. I'd rather know what they intend when faced with a wall of fog (slam the door? charge in anyway?) before checking initiative. If they act before the enemy and choose to close the door, I don't want to give away the presence of an enemy by them having already rolled an initiative.

I'd like to be able to use an illusionist-type opponent against the party, but I'm stuck with the fact that they are recognisable as illusions.
Here's another idea - the enemy can cast 8th level spells. Quickened Major Illusion of a wall of stone, followed by a Prismatic wall right behind it. Since the party has no reason to doubt the nature of the wall of stone (unless of course making the spellcraft roll constitutes knowing that it's fake, and thus getting a roll...) the caster wouldn't hear the second spell being cast. If she yells that the wall's an illusion, I get to fry the first player to try to walk through the wall.

By the way, what kind of roll would you give someone to avoid a prismatic wall directly behind an illusionary wall they've declared they are running through? Would you even allow a reflex save to avoid blundering into it?

[Cyrion]

If they see the casting, I would give them the normal spellcraft roll to ID it as an illusion, but otherwise they have to interacti with it.

I also wouldn't have the illusionary wall of stone muffle sound. That would be one clue that the wall of stone isn't real. However, I probably wouldn't tell the player that the character can still hear. They'd have to ask the question.

One easy way to solve the initiative roll problem is to roll initiative for the next encounter as part of the clean-up from the previous encounter. As the party's tallying treasure, healing, etc. just have them roll the next initiative and save it for when you need it next.

Unless they give me an indication that they're checking ahead of them, I probably wouldn't give them much of a save at all. I might add a chunk to the DC so that it's difficult but still makeable, but then tie how many layers they try to plough through based on how much they make their save by. Make it by 1 and you stop before the last layer. Make it by 2 and you miss the last 2...

[The Glyphstone]

@Prismatic Wall: I can't see any reason why you would deny them saves to begin with - you can deliberately walk head-on into a Prismatic Wall, or even run through it, and still get a save. I suppose with the argument that you didn't know it was there, but then there's the problem that being Blind doesn't deny you the ability to save against a Prismatic Wall either.

[Yukitsu]

I think he means a save to not run into it at all, which they shouldn't get.

[The Glyphstone]

Yeah, that would be fair. In that case, I'd make them automatically save against the layers of the wall in the normal order, and as soon as they passed one, give them the choice of trying to punch through the rest of the way, or pulling back to this side of the wall.

[erikun]

For rolling Spellcraft, what do you do if the BBEG starts casting a fireball? Do they players automatically roll a Spellcraft check, or do they roll only if they ask what he's casting? I would just treat it like any other spell, although if they know that it was an illusion being cast, they have the +4 to saves like against any other known illusion.

The illusionary Wall of Stone should only muffle sound if the spell cast can affect sound. You can hear right through a Silent Image Wall of Stone, but sound would be muffled through a Major Image Wall of Stone. (The fact that you can still hear talking through 5' or stone may hint that it's an illusion, though.)

For fog in the room, interacting with an illusion allows a save, which includes standing in it's effect. If they're walking through the illusionary fog, they automatically get saves.

I generally don't have players roll initiative unless they're getting ready for combat. If they're being stalked by something (invisible wizard, hidden rogue) then I don't ask for initiative. Of course, if they pull out their weapons and start looking around, I have them roll as normal. (No surprise round on them, either.)

For 3.5e, an illusion that is saved against still appears "as a translucent outline" that can be seen through. If they saved against the illusionary Wall of Stone, then they'll be able to see the Prismatic Wall behind it. If they didn't save against it, then they couldn't charge through the illusionary wall anyways. (Their subconcious mentally stops them from running through it. They could still jump through, though, if they were feeling gutsy. No save that way, though.)

[KillianHawkeye]

On a similar note - if an enemy has an illusion of fog filling a room (and is in there), and the party open the door, how do you resolve it? Initially neither side was aware of the other, so no surprise round, right? So an initiative roll is called for, but if I ask for an initiative roll it opens the door to metagaming. I'd rather know what they intend when faced with a wall of fog (slam the door? charge in anyway?) before checking initiative. If they act before the enemy and choose to close the door, I don't want to give away the presence of an enemy by them having already rolled an initiative.

A room filled with fog isn't an encounter. An encounter doesn't begin until one or both parties become aware of the other. Thus, if neither side is aware, there's no need to roll for initiative yet. Just describe the fog and see what they do. Eventually, one side will notice the other and then you can call for initiative.

Anyway, if the enemy in the room knows the fog is an illusion, he can probably see through it and will notice the door opening immediately. So there probably would be a surprise round in this case, although the enemy may not do anything to alert the PCs until they are within the room by holding his action, moving silently, casting a silented spell, etc.

[ghashxx]

It is for precisely this reason that I hate illusions, so complicated. I'll start off with the fog. The caster can see through the fog because he knows it's an illusion. So when they open the door the caster knows they're there while they are still clueless. So the caster gets a surprise round, then everyone rolls initiative afterwhich the players have to try and figure out what's going on, and battle starts. That's the thing, the caster isn't affected by his own illusions unless he wants to. Where this get's crazy is with shadow spells, like a shadow spell imitating an enhancement. There's a thread somewhere around here about that stuff, and it's nutso.

[Epinephrine]

Thanks - I guess I'll have to use some stilled/silenced spells if I want to be assured of being able to hide the actual spell types. I guess I'll give the enemy a surprise round. That will at least allow him a chance to put up a defence.

[Kurald Galain]

How, as a DM, do you use illusions versus your PCs? Inevitably there will be party members who have spellcraft, and will recognise illusion spells as they are cast. Isn't this a HUGE weakness?

Yes, it is. That is why a clever opponent will not cast such a spell in plain view. Overall I am of the opinion that you shouldn't tell players that an illusion is nearby unless they have a reason to suspect something is wrong, and then give the players subtle clues until they do realize something is up. I know that this is not exactly according to RAW, but it's more fun to play it this way.

So an initiative roll is called for, but if I ask for an initiative roll it opens the door to metagaming.

That is easily solved: have everyone roll initiative at the end of combat (or, the beginning of the session) and use those values whenever the next combat begins.

[The Gilded Duke]

Depending on the battle they might have to make a listen check to hear the vocal components of the spell.

Assuming the illusionist was speaking at normal volume, it would normally be a DC 0 Listen Check.
If the listener is distracted (say by a battle) the DC goes up by 5.
The DC also goes up by 1 for every five feet away the sound is.

Silent Image has a range of 400 +40 feet per level.
At first level that could make the Listen Check DC as high as DC 93

A spot check isn't quite as hard to do, while distracted makes the DC +5, you only get +1 to the spot difficulty for every 10 feet, making the DC go up to DC 49

According to the spellcraft entry, you can only make a spellcraft check to identify a spell if you can see or hear the spells verbal or somatic components.

The above DC's assume that the spellcaster isn't invisible or trying to hide which could easily bump up the spot check 20 or more points.

[ghashxx]

When it comes to the spellcraft question I find players very rarely actually use it. After all, what's the use of knowing it's a fireball when knowing that doesn't help you dodge. So unless you auto spellcraft for them, or they always do that, then don't worry about it. Also, being told it's an illusion doesn't auto save, it just means you've been told that and now you have to truly believe it's an illusion. It's like the Matrix, just because you know it's all not real doesn't mean you get to do anything you want unless you "truly believe".

[Kurald Galain]

It's like the Matrix, just because you know it's all not real doesn't mean you get to do anything you want unless you "truly believe".

Oh yeah, and let's not forget the old rule that an attempt to disbelieve automatically forfeits your saving throw if the effect happens to be real.