A few years ago, my party were trying to liberate a dwarven mine from the forces of the Scarlet Brotherhood. As they emerged from the mine, they found soldiers waiting for him.

Ever quick-thinking, the wizard created the illusion of a great demon emerging from the mine behind them.

Ever not quick-thinking, the paladin turned around and charged the demon, as he didn’t realise that his friend had created it!

That encounter didn’t end so well – some of the players escaped, others were captured. A prison break was thus needed!

Illusions are part of the game that allow casters a wide variety of options, and potentially break the game if ill-used. Polymorph, charm and wish spells also have this incredible variety of effect – it’s not something that, like a fireball or magic missile spell, can be easily quantified.

Reams of advice on illusions have been published over the years. The original illusion spell was a second-level spell called phantasamal forces, reproduced here:

Phantasmal Forces: The creation of vivid illusions of nearly anything the user envisions (a projected mental image so to speak). As long as the caster concentrates on the spell, the illusion will continue unless touched by some living creature, so there is no limit on duration, per se. Damage caused to viewers of a Phantasmal Force will be real if the illusion is believed to be real. Range: 24”.

Gygax, Gary and Dave Arneson, 1974. Dungeons & Dragons. Volume I: Men & Magic.

By Advanced Dungeons & Dragons, the spell – now called phantasmal force – had been increased to third level for magic-users, but the new class of the illusionist had it as a first-level spell. A little further clarification was given in this edition.

When this spell is cast, the magic-user creates a visual illusion which will affect all believing creatures which view the phantasmal force, even to the extent of suffering damage from phantasmal missiles or from falling into an illusory pit full of sharp spikes. Note that audial illusion is not a component of the spell. The illusion lasts until struck by an opponent – unless the spell caster causes the illusion to react appropriately – or until the magic-user ceases concentration upon the spell (due to desire, moving, or successful attack which causes damage). Creatures which disbelieve the phantasmal force gain a saving throw versus the spell, and if they succeed, they see it for what it is and add +4 to associates’ saving throws if this knowledge can be communicated effectively. Creatures not observing the spell effect are immune until they view it. The spell can create the illusion of any object, or creature, or force, as long as it is within the boundaries of the spell’s area of effect. This area can move within the limits of the range.

Gygax, Gary, 1978. Advanced Dungeons & Dragons Players Handbook.

The limits of the use of phantasmal force depend entirely on the imagination. And, of course, was the bane of Dungeon Masters everywhere, as the ingenuity of players is often far more than the Dungeon Master can handle.

I tend to think that the first time someone uses an effect, it’s cool. “We create the illusion of a demon”. “We create the illusion of a pit full of spikes”. “We create illusionary wings on our backs!” (That last, though cool, likely wouldn’t work so well…) However, with repetition, the coolness wears off. It moves to mundane. And, often, into the “this is tremendously overpowered” drawer.

One of the paradoxes of these sorts of spells – monster summoning, polymorph, wishes, illusions, and so on – is that the more you try to codify them in the rules, the more problems they give the game. People like following the rules. So, if you’ve said “you can summon eight challenge rating 1 monsters with this spell”, then someone is going to find the most broken challenge rating 1 creature, and summon it.

Alternatively, the spell is reduced in power so much that many believe it no longer is worth taking. Take a bow, sleep and charm person!

Dungeons & Dragons 3rd Edition gave very detailed rules for determining the Challenge Ratings of monsters and advancing them. They were broken – badly. The designers at Paizo kept those rules during their creation of Pathfinder 1st Edition. I saw several official adventures that followed those rules – and had the most overpowered and underpowered monsters you can imagine. Colour me unimpressed.

This is why Dungeons & Dragons has a Dungeon Master. It’s so that they can adjust the game based on what’s actually happening rather than what a rulebook says – as a rulebook does not understand the context that the rules find themselves in at a given table.

So, if the Dungeon Master has to rule on these things, what should they do? My basic rule:

• If it’s the first time something’s been used (and it’s cool!) it works
• If it’s the second time it’s been used, it mostly works
• If it’s the third it’s been used, it’s time to judge how it feels in the game: Overpowered? Underpowered? Just right?

If something feels right, you don’t have to change it! Hooray!

If something feels underpowered, then the player will either (a) stop using it, or (b) suggest to you it become more powerful.

If something feels overpowered, then it’s time to start thinking about how to fix it. If it’s a core piece of the rules, then do some research as to how other people handle it. (For instance, for monster summoning spells, many DMs choose the creatures summoned rather than the players. This gets away from the circle of pixies problem!)

Your goal isn’t to nerf it into oblivion, though. If something is overpowered, you want to just get it back to “powerful”, so the player doesn’t feel like they’ve wasted their time taking the option.

Most importantly, reward imagination and creativity. If the player falls into a rut – always using “I create the illusion of a meteor swarm and burn them all to a crisp!” for example – then that technique should fail sooner rather than later. If a player keeps surprising you (and the other players) with their inventiveness, then allowing it to continue is likely the best idea.

Of course even if you do allow the spell to work, there may still be side effects. The best thing about the paladin running back to fight the illusionary demon was that it was a limitation on the spell created entirely by the players! Ask your group what to do! They may surprise you with a solution!