Running an illusion based enemy?

Hey guys, long time no see.

My group and I are into full swing now on our campaign and I’m getting really excited for when they start piecing things together. I’m fortunate in a way that my PCs aren’t familiar at all with D&D lore so I can drop in monsters and they genuinely have no idea what they are and therefore no ability to metagame.

One such monster that I’ve name-dropped is an Illithid. He’s going to be one of the big bad’s generals (though they seem to think he is the big bad currently)

So my question is this - how would you guys run a fight with an Illithid in-game? I really struggle with illusion-based encounters because once the PCs know they’re fighting illusions they start to take leaps of faith and just ‘walk through’ the illusions acting like there is no real threat.

Also two smaller but still related questions:

  • Would you have phantasms deal physical damage, say if a character was struck by an illusion they thought was real?
  • Phantasm states that it can be resisted like any other bane but if the Player/Character doesn’t know it’s not real, do they not get a roll? Is this roll the character trying to figure out whether the thing is real or not so they need some initial doubt before being able to make it?

The thing about illusions is that they’re supposed to be something you can walk through if you know it’s not real, an illusionist combatant is something of a glass cannon in this regard. My advice would be to take a look at related Banes, like Fear or Dominated, in order to make the fight more interesting after the illusion is broken.
With regards to Phantasm:

Definitely, if you like. Remember that HP is not Health, it can represent mental damage or just becoming demoralised as much as it can represent cuts and bruises.

Any time the character takes a resist action, they can resist against all Banes on them whether they’re aware of them or not (that’s how I rule it anyway). You can make the roll for them if you don’t want to give it away. Alternatively, you could allow them to resist whenever they get suspicious about the behaviour of the illusion, anything that might give away that it isn’t real.


That’s a fair point but I think my players often struggle with differentiating between what they know and what their characters know. For example, once my players know they’re dealing with illusions they send their characters into them without any concern, taking a leap of faith because the player knows that it’s not real and they will continue to do this with every other illusion they come across in that encounter.

I think my problem with this is that if it’s a social illusion, say a Phantasmal guard has been conjured to talk to the players and throw them off the trail of an investigation, it seems very odd to tell them to do a resist roll (or even for me to do it for them) if the Phantasm roll has already beaten their Resolve on invocation. So should a combat Phantasm be treated differently just because it can cause harm?

I’m leaning towards ruling it so that in order to make a resist roll (assuming the invocation is higher than the target’s resolve) they must have a reason to doubt what they’re seeing and if they fail that resist roll - even if the character is now aware that they’re dealing with an illusion - it means that their subconscious mind is still perceiving the threat as real.

“If the roll is greater than or equal to their Resolve, they perceive the illusory effect you create and react as if it were real.”

Only once a successful resist roll is made are they considered to have summoned the mental fortitude to overcome the illusion and then they can walk through it harmlessly.

My concern is that this is too strong but I think the alternative (resist rolls with no insight that they’re seeing an illusion) is potentially too weak.

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I think you might have misunderstood me here, I wasn’t saying to randomly resist phantasm even if they weren’t aware of it; I meant if they’re choosing to take the resist action anyway (because of other banes) then they/you can roll for phantasm as well.

I also allow players to choose to resist if they’re suspicious (even if it’s not an illusion) as you suggest, the above is just my interpretation of how the resist action works. That seems entirely sensible to me, and your interpretation of them being able to walk through it is correct; it depends on the method that phantasm is being invoked with as to whether it just disappears or whether they can simply see through it.


Ah my bad, that makes a lot more sense. I think Phantasm is pretty unique in the sense that you’re tricking the players and they can be completely unaware that anything is happening to them.

I think this is one of the best ways to handle it - don’t tell the players what they’ve fallen victim to but do allow them to ‘test’ what they’re seeing with a speculative resist roll.

Remember about Bane attacks. Damage isn’t the only thing monsters can interact with players. Fear, immobile, basically everything that target resolve could be handy. If an action takes place in limited space, like a cave for example, illusion of stone wall or abyss, even you can create another encounters using just Phantasm. Think what is a, i don’t know how to better enclose it, target of Illithid. Does it feels lonely and doesn’t wanna let players go or just want to drive them mad. Your story, your creature. Make it deep and unique :smiley: