Can the Phantasmal Force spell knock and hold someone prone?

Question

The description of the Phantasmal Force spell states:

You create a phantasmal object, creature, or other visible phenomenon of your choice that is no larger than a 10-foot cube and that is perceivable only to the target for the duration. [...]

The phantasm includes sound, temperature, and other stimuli, also evident only to the creature. [...]

While a target is affected by the spell, the target treats the phantasm as if it were real. The target rationalizes any illogical outcomes from interacting with the phantasm. [...] An affected target is so convinced of the phantasm’s reality that it can even take damage from the illusion. A phantasm created to appear as a creature can attack the target. Similarly, a phantasm created to appear as fire, a pool of acid, or lava can burn the target. [...]

Let's say I cast Phantasmal Force to create phantasmal red hot chains that come out of the ground, gripping each limb and dragging the target down. If the target fails its Intelligence save, would it now be prone and taking 1d6 damage?

Answer 1

There is no RAW answer. It must be decided by the DM.

Firstly, this ambiguity is likely an intentional, direct consequence of 5e's design ethos of "rulings over rules" and the prominent role of the DM as the person that must make those rulings in the case where the rules are silent. Illusions and illusion magic are one area in which there is essential no general rules guidance, and thus falls squarely into the domain of DM-rule.

Jeremy Crawford said as much when asked about this exact question on Twitter:

Q: Can a creature under the effects of Phantasmal Force be restrained by it, i.e chains wrapping around a creature?

A: Phantasmal force details the few game effects that it can reliably create. A DM is free to allow additional effects.

Because illusions are a complicated issue, I will outline two of the major DM approaches to this issue. Since they take opposite stances to each other, any DM reading this will have to figure out which way makes the most sense, seems the most fun. and/or which way aligns better with how they've already been handling it.

The core of the disagreement is whether the DM rules that an illusion fools the mind so thoroughly that the body will react physically to it or not.

Interpretation 1: No, Phantasmal Force cannot chain someone and force them prone

In this argument, the spell looks and feels like a chain, but the chains (not being real chains) would not be able to restrain the creature since they would offer no resistance when the creature tries to struggle out of them.

The target rationalizes any illogical outcomes from interacting with the phantasm

Because of the above effect from the spell, the mind of the creature would try to rationalize this in some way (the chains broke, the chains loosened temporarily, etc.) but they would still believe the illusion to be true.

In this way the creature would not gain the prone condition because their movement is not actually inhibited in any way even though they believe the illusion is real.

See this answer for a more thorough take on this interpretation.

Interpretation 2: Yes, Phantasmal Force can chain someone and force them prone

In this interpretation, the chains really do restrain the creature because the creature treats the chains as real chains, even though they are not.

While a target is affected by the spell, the target treats the phantasm as if it were real.

The chains also sound and feel real to the target in every way.

An affected target is so convinced of the phantasm’s reality that it can even take damage from the illusion.

So, in this case, when the creature tries to escape from its restraints, its mind, thoroughly convinced that the chains are real, will act under that assumption. Thus, the creature's limbs will be bound. And this creates the case for the fact that the creature is able to gain the restrained condition from this spell.

See this answer for a more thorough take on this interpretation.

Decide but stay consistent

So I have provided very brief overviews of two interpretations of the spell's effect. There are certainly more of them out there. As a DM, the key is to decide on one and apply it fairly, transparently, and consistently. Not only across this spell but other similar ones.

Answer 2

Yes, it can make the target think it's being held prone

Disclaimer: All instances of real/reality used in this answer are with respect to the target thinking they're being affected. Phantasmal Force does not have the capability of actually creating something tangible, only to appear to be tangible to the afflicted target.

I've emphasized the important bit in the spell.

While a target is affected by the spell, the target treats the phantasm as if it were real.

Obviously this speaks to the reality of the spell.

A phantasm created to appear as a creature can attack the target. Similarly, a phantasm created to appear as fire, a pool of acid, or lava can burn the target.

That part details that whatever you describe can function as it normally would if it were real.

An affected target is so convinced of the phantasm’s reality that it can even take damage from the illusion.

And that part reinforces it all over again.

The phantasm includes sound, temperature, and other stimuli, also evident only to the creature.

That's the part where the illusion actually feels real to the affected target. This means that the chains, for all intents and purposes, are real to the target. Up to and including touch.

Obviously the writers couldn't outline literally every single illusion you can conceivably cast, so you have to extrapolate a bit. The three quoted parts above clearly demonstrate that the phantasm, for all intents and purposes, functions in whatever manner you describe as if it were real.

The balance is built in with the damage caused by the spell. It doesn't really hurt that bad at a meager 1d6, so using it as a means of crowd control is a far more effective and creative use.

So what can you do with this spell?

Well, you can't create things that are actually real, so you couldn't get a creature to cross a bridge no matter how hard it tried. It would simply keep falling and chalking it up to earthquakes or something.

However, in my opinion, if the creature is capable of performing the action without an external force acting on it, like being restrained by hot chains, then that is definitely within the bounds of the spell. It requires no contradiction and no actual force because the creature will act as if it is restrained.

This is reinforced by the last sentence of the spell:

The target perceives the damage as a type appropriate to the illusion.

This statement means, quite clearly, that the affected target is perceiving the pain of being afflicted by whatever illusion you cast. That, coupled with all the statements in the spell that treat the illusion as if it were real, and the stimuli accompanying the illusion, make it so that the illusion for all practical purposes, counts as real for the target, and the target alone.

Answer 3

No, phantasmal illusion can't knock or hold someone prone

The target rationalizes any illogical outcomes from interacting with the phantasm

The objects created by the phantasm are still illusions so they will not actually restrain/bind/grapple/whatever other status you want to use to hold them prone.

Say, for example, you created chains to bind the target. To the target these chains appear totally real, they can see them, they can feel the metal, they can see they are totally bound. But then the target tries to move. They strain mightily against their chains and.... their movement is totally unimpeded. The spell is still working so the target envisions it as bursting the chains, or the chains crumbling, or any other way as long as it matches up with the reality that they can in fact move. The chains are only an illusion so when the target tries to move.... they move. They wouldn't be taking damage unless there is a logical reason the chain could hurt them.

Another example would be a phantasmal flaming wall that appears over the prone target. The wall being made of fire is a good incentive for the target to stay prone and avoid being burnt. However they could choose to stand up if they wished and move through the wall. It would still cause them damage (1d6 as noted in the spell) either way.

For a final example let's say you created an illusionary creature to knock the target prone. When the creature tried to push the target the target would notice they are not actually knocked down. They would rationalize it and assume the creature missed, that they pushed the creature back, or some other way of explaining why it didn't work. They would continue taking damage as noted in the spell.

Answer 4

No, a character cannot be knocked prone or restrained by Phantasmal Force.

There is no text in the spell description that states the affected creature can be the subject of any mechanical conditions. What is stated is that it treats the illusion as real despite any contradiction, which will be rationalized away. Spells are restricted to doing exactly what they are described as being able to do.

Contradictions such as being able to see an ally through a wall are rationalized away. Being able to hear despite a fog horn blasting is rationalized away. Being able to move freely despite being engulfed by red hot chains is rationalized away. Being able to charge cage bars and pass through them is rationalized away.

Admittedly odd scenarios arise from this, such as a creature refusing to attack a real creature that it believes it can't see, while mechanically having vision of it. Rationalizing this contradiction is left as an exercise for the reader.

Answer 5

A simple solution if the DM says no, is to team up with another spellcaster and have them cast something like web or hold person/hold monster while you cast phantasmal force. That way the illusion is reinforced by the hold/restrained effect. I myself would say yes for this, as it is a psychosomatic affliction and thus the mind rationalizes that they can't move due to the illusion. But to each their own.