Updated: Mar 18, 2019
"A perusal of the number and types of spells usable by illusionists (see CHARACTER SPELLS) will reveal that they are at least as powerful as normal magic-users and possibly slightly more potent at very high levels."
PHB p. 26
I have, up until now, managed Illusions without seeking third party advice. It is somewhat fitting, in a perverse way, that the rules surrounding illusions are themselves often hazy.
Additional parameters for these vague spell descriptions seem tricky to design. I'm not talking about Detect Invisibility, Hypnotism or Wall of Fog here.
I'm talking about Phantasmal Force and how it generally gets worse from there.
Here's a snippet of speculative fiction:
DM: "A pit opens under your feet, you are too far from the edge for your dexterity to be useful. You fall into it.
Player: "So lame."
DM: "You fall and take (rolls 2d6) seven. Seven points of damage. You're ankle is sore but now you realize that you didn't fall at all. The stone floor is smooth and devoid of traps. Perhaps it was an illusion."
Player: "How was I supposed to know it was an illusion?"
DM: "You weren't. That's the point. You have to say you disbelieve in order to get a saving throw."
Player: "Even more lame."
I don't know if this conversation has, in fact, ever happened. But odds are high.
Illusions pose a challenge for players and DMs alike. While conscientious players (the likes of which I play with regularly) may try to avoid abuse, there is always the question of, "How far can I [or should I] push this?"
When the sky is the limit, creativity usually foregoes extravagance and distills down to the most efficient means to an end. In the case of Spectral Force, that might be a reeking 10'x10'x40' deep pit lined with poison-coated spikes...or an illusory copy of the magic-user's fireball (cast last round)...or maybe just a scything blade taking off the victim's head. Sure. Why not?
Strangely, the specific nature of the illusion is likely to be unimportant as the illusionist in question is often simply trying to describe the most lethal thing they can think of. Though the illusion of a mass of ropes surging around the target, cinching it tight, is useful when non-lethal means are desired, we arrive at similar problems.
The first is, how do we tackle the unreliable narrator when it is the DM we are talking about?
Players will always be suspicious of what the DM says when he or she is voicing an NPC, or describing an empty room. This is because they know there are evil-doers and traps in this world. But when the DM describes an actual threat, players generally don't second guess.
Many grognards worth their salt will tell you THAT'S the process of learning and that eggs must break along the way. Certainly player's acting cooperatively, tactically, intelligently, is the goal of any good game. And players do quickly learn to listen at doors, check for traps, extinguish the light, etc. They also learn to use fire on a troll for instance. But is there a lesson to be learned in the face of illusions?
I would argue that telling players the door creaks open on an empty room IS mechanically different from telling them that three wyverns have swooped down and to please roll for surprise.
In the first case, the DM is conveying information about something that MIGHT be true. Similarly, when the DM says that Buddy the Barkeep claims to know nothing about their missing gear, it is something Players intrinsically suspect MIGHT or might not be true.
But when the DM describes an active threat, the acid is poring through holes in the ceiling, the viper is lunging, the shadowy figures have already encircled them, Players are TRUSTING the DM to be asking for action, for quick and intelligent action no less. Because the point of D&D is that. The point of D&D is NOT to go through a mindless list of, "I listen; I check for traps; I disbelieve."
Imagine if every combat, trap, or magical event started out with the party shouting, "I DISBELIEVE!"
Option #1: The DM describes the incredible blue flames unfurling in the air around a dragon-like demon of magenta gemstone; describes the crack of the whip...the cackle in the throat below that toothy maw. The DM describes the smell of cooked ozone closing in around the party and then says, "but there seems to be something off about it..."
Wow. So, not a very good illusion after all, right? The players all get a saving throw, those that succeed pass a +4 bonus to their friends on round 2 and we go from there. In this case, illusions might fool some of the characters, but NONE of the Players...and that's emotionally lame.
Option #2): The DM doesn't provide any tells. He or she telegraphs nothing. And guess what? A couple of eggs break. After one or two characters have died in the illusionist's tower, the Players are chanting "I disbelieve," every 10'.
Neither of these are to my liking, but I have seen and used both methods. Both fail to take into account the ability scores of the characters. Both approaches also fail to elevate the level of play. Disbelieving is simply THE way to deal with illusions, unless you have detection magic. And even then...Spectral Force includes thermal, so Infra will be fooled.
Whether Detect Evil reveals that there are no wights present is problematic because there are many ways to mask creatures from divination. Are the wights so warded or is this really an illusion? In the Illusionist's tower, your players WILL be shouting their disbelief every 2 minutes and your game will probably devolve over the course of the night.
If you run a dungeon with hidden traps every 10', you will wind up in the same position, with endless trap checks, with frustration and a general sense of unfairness. Illusions are, in some ways, worse because they are the focus of an entire class and therefore have legs.
This led me to thinking about how to make the illusion fair AND support the claim made in the PHB, that the power of high-level illusionists might exceed that of arch mages.
Hand in hand with this is, if we understand the intentions of Players honestly, how do we balance the notion that every saving throw vs a well-made illusion is potentially a save vs death? "Sorry, bro. Two-ton block appears above your head and crushes you. Roll a new guy." Does it even make sense, in this light, to NOT give a saving throw to a PC or NPC that did not explicitly disbelieve?
Spoiler: my answer for this turned out to be "sometimes".
I did no research into how others might have solved this problem before writing this post. Instead, I simply reminded myself of the lethal nature of AD&D, it's vorpal swords and spheres of annihilation. Then I turned to my design instincts and consulted with the player currently playing an illusionist in my campaign.
Illusionists are incredibly powerful against a certain demographic: creatures that can see and are not immune to mind-affecting magic. Since illusionists are going to be hamstrung in some of the most popular adventuring locations, they need to feel powerful when they face susceptible targets and the DM needs a way to fairly embrace lethal illusions and determine whether they are believed or disbelieved.
My design filters:
Illusions must be less effective on creatures of both very high and very low INT. The former notice inconsistencies and see through them, the latter simply don't process them (think of the way an animal may not respond to images on the TV).
Illusions must pose the very real AD&D-intrinsic threat of death
Phantasmal Force must be significantly less effective than Spectral Force (level significance)
To these ends I created a chart that would tell me when to roll a saving throw vs when to let the illusion have full sway. I think of it in the same way I think of the elf's passive ability to notice secrets.
The player running an illusionist in my game looked over the table I created. We decided it was good enough for testing. Here is the version we'll be starting with.
The top row is spell-level
The left column is INT of target
Numbers indicate the % chance of automatically getting a saving throw in the face of an illusion
Asterisks indicate total immunity to illusions of that spell-level (per Deities & Demigods).
Ergo, Bijan casts the illusion of a 40' deep pit opening below Mike-the-NPC-fighter's feet. Mike has an INT of 11. Bijan's spell is 2nd level. If the DM secretly rolls 46 or less, Mike is allowed a saving throw (even though he did not declare that he disbelieves the pit's existence). If Mike then makes his save, he sees the illusion for what it is. It's fairly likely that Mike will fall 40' in his mind and die because it is fairly likely he will NOT be given a saving throw. However, the same spell cast at Mortimer the magic-user (18 INT) is 98% likely to allow an automatic saving throw vs the illusion.
So, how do I plan to test this?
I plan to provide no tells about an illusion's existence, conduct the roll in secret and then ask for a saving throw vs Spells. Failure = full brunt of the illusion. Success = all other characters can be immediately notified of the illusion and are automatically allowed saving throws to disbelieve. Such informed saving throws get the normal bonuses (+4 for being notified plus any WIS bonuses).
If a player explicitly declares that they disbelieve WITHOUT having been notified, rather than granting them a saving throw immediately, I will instead consult the chart and probably toss on a bonus 10%. Again, this is not tested yet. Clearly, guys with 5 INT should not go up against Illusionists...but doesn't that kind of make sense?
Now before you go off about how insta-kill this is likely to be for low-INT folks, I agree. But I think it should be. Keep in mind, however, that magic-resistance should still apply and simply closing one's eyes will neuter most illusions in exchange for attacking at a -4 penalty. Clever parties might even blindfold their dumber members, potentially wrecking that evil-illusionist-tower-adventure you designed.
Unless your evil illusionist happens to know this spell I made specifically for him:
Area of Effect: Special
Casting Time: 3 segments
Saving Throw: Neg.
Explanation/Description: This spell affects a 2"x2"x2" area and any number of creatures whose total HD are equal to or less than twice the illusionist's level. All affected creatures that do not save have a magical eye opened, usually upon their head, or anywhere that the illusionist desires.
This eye cannot be closed, sees clearly even in total darkness and cannot effectively be blindfolded by any means. Although the spell will not affect creatures immune to mind-affecting spells (such as undead) it can cause normally blind creatures to see and is in fact a direct channel to the illusionist's magic. For the duration, affected targets will certainly see any and all illusions the illusionist casts, even if they close their eyes, turn away, cast darkness, hide behind shields, or bury the eye in the sand. All saving throws against illusions/phantasms during this time are penalized by -1.
Note that the spell is temporary and does not cure blindness. Sightless creatures will be sightless again when the spell expires.
So there you go. Full speed ahead with play-testing this new table, which I hope will bring some consistency to whether or not monsters (in particular) decide to disbelieve in the PC's illusions. But equally, I hope it makes explicit to Players that there is a method and an honesty to detecting illusions that is based on their Ability Scores even if I don't telegraph it in my description. Not leastly, I hope it underscores the assertion in the Player's Handbook concerning the power of illusionists and the real dangers of the visions they weave.