D&D 5E How does the Phantasmal Force spell work correctly?

[lkwpeter]

Original Post:

1.) I read a lot about "casting a black container around a creature's head" so that the creature is blinded. Or "casting some loud noises to it's ears, so it is deafend". But is that really possible?

2.) Also I would like to know, how creatures act that I cast. For example if I want to make a hostile creature beliefe that his boss is talking to him and wants it to leave his guard post. Can I interact with the illusion or change things after I cast it?

3.) What other restrictions are there? And what is the best use of it?

EDIT: The following is a personal summary of this forum thread:

Please note, that I don't claim this to be the only way of interpreting the rules. Phantasmal Force is very vague and this thread was a try to find an interpretation that is consistent with the wording of the RAW and that is consistent in analogy to other spells. These are just the main agreements of this discussion:


Effects:

• If you create a person, you do not need to know the language/appearance of the it. Like I'm a Banana said, "It's not like the illusionist is making the illusion say something, it's like the illusionist is saying, "get this concept across" and the target's mind shows the target what the concept would look like from the target's perspective. So, it relies on the target's sense of what's possible, not the illusionist's. That's part of why they're just single-target.". Furthermore this is not part of the spell's description, although some other spells explicitly say so.
• You can also create phenomena. And those can even cause status effects (e.g. blinded). (see Jeremy Crawford's Tweet here)
• Like Jeremy Crawford approved, created objects will move with the target and can also cause status effects (see his Tweet here).
• Analogous to that, if you create a hostile creature that is attacking the target, this creature would not be bound to its position. Instead, it would also follow the target, if that is trying to escape, etc. The reason is, that the creature is within the target's mind, so it won't be stuck to a position. Consider that only the "conjured" creature must be not larger than 10 foot, but not the area that it is able to move within.
• Physical interactions do NOT reveal the illusion! The reason again is that the illusion is within the target's mind. That is very different to other illusion spells.

Restrictions:

• The object must be visible for the target (spell description). So it can't be invisible.
• If the illusion is not reasonable to the target, it will probably investigate it. Consider, that illusions that look like magical spell effects are hardly "not reasonable", because the target would normally think that it's a "normal" spell effect. Contrary to this, if the target's mom that has died years ago suddenly appears in front of it, the target would probably "resist" the illusion and investigate it (as an action, after it failed the initial INT saving throw).
• After casting this spell, there is no further interaction with the illusion possible: Like Storyteller Hero said, "the phantasm can act as you "pre-program" it." The caster can neither see the illusion himself, nor can he change or interact with it after he casted the spell.

Controlling creatures (shackles, cages, etc.):

• The most important point is: This spell is a psychic force, no physic force! So, it is not possible to physically control a creature! If you create chains to bind it, these might even move a bit with the target. But the moment, the target moves away from the object, its arms/legs would simply go through the illusion. The creature would rationalize it in some way (as the spell description says), but it would be free though.
• Instead, you could try to affect the creature's motivation to do something: E.g. you could create a cage of fire. The creature might feel the heat an decide not to touch it. Or you could create something that forces the target to go prone at its own will (e.g. a poisonous fog at a specific height, so that the could duck).
• Apply the following rule of thumb to find out, whether or not a specific object would work to control a creature:
  1.) "Is the object supposed to physically affect a creature?" If yes, the effect is not possible
  2.) "Is the object supposed to only affect the creature's motivation to do something?" If yes, than it is absolutely viable and works as the spell is intended to work.

When does Phatasmal Force allow a INT (Investigation) check?

This is tough question, because the spell's description says: "The target rationalizes any illogical outcomes from interacting with the phantasm." That means two things:

1. The target rationalizes everything from interacting with the phantasm (and only with the phantasm).
2. The target rationalizes inconsistencies only from interacting.

For this reason, external influences could be one reason that raises doubts. But keep in mind that other creatures don't see the illusion!

 

[Plaguescarred]

These looks like fine uses of the spell! There are many possibilities to use a phantasmal force to hinder or injure a target if wanted.

Creating the illusion of bindings like a straightjacket to cause target to be restrained or paralyzed could also be another useful use to pin it down.

Or creating the illusion of a skin rash infection that provoke itches and scratching causing pain (1d6 psychic damage/round for up to 10 rounds)


Yan
D&D Playtester

 

[Storyteller Hero]

Hey,

1.)
I read a lot about "casting a black container around a creature's head" so that the creature is blinded. Or "casting some loud noises to it's ears, so it is deafend". But is that really possible?

2.)
Also I would like to know, how creatures act that I cast. For example if I want to make a hostile creature beliefe that his boss is talking to him and wants it to leave his guard post. Can I interact with the illusion or change things after I cast it?

3.)
What other restrictions are there? And what is the best use of it?


Thanks in advance!

1. Yes, the phantasm can move around with the target and take up its line of sight since it's in the target's mind. SAGE ADVICE

2. The phantasm can act as you "pre-program" it to do so, including attacking the target (specific damage in the spell's description), but it's going to be based off of YOUR memories/imagination of what it's supposed to look or sound like. Only the target can perceive it, you can't change it after casting.
SAGE ADVICE

3. Your caster can't accurately make something if he/she has no idea what it could look like, like the starship Enterprise for example, or the target's mother whom you've never met before.

 

[jaelis]

And what is the best use of it?

I like effects that seem reasonable for the situation, so that the the target isn't tempted to use its action to investigate. Like, a cloud of darkness is cool, but some creatures might find it surprising and investigate. For a target that knows about magic, duplicating an effect of another spell can work though. For instance, a cloudkill-like effect could obscure vision and do some damage. For unintelligent creatures, various types of traps can be good, like a bear trap anchored to the ground to damage and restrain.

The example in the book of using it to disguise an actual pit or other trap is probably one of the best though.

It also has a ton of out-of-combat applications, though a lot of them can be done with other illusion spells too.

 

[Lanefan]

Only the target can perceive it, you can't change it after casting.
SAGE ADVICEThe caster can't see her own illusion? Bizarre ruling!

Lan-"not surprising, though, in that illusions have been getting mostly less and less useful with each passing edition"-efan

 

[jaelis]

Only the target can perceive it, you can't change it after casting.
SAGE ADVICEThe caster can't see her own illusion? Bizarre ruling!

Lan-"not surprising, though, in that illusions have been getting mostly less and less useful with each passing edition"-efan

Phantasmal force has always worked that way, no?

Ah no, sorry, I'm confusing it with Phantasmal Killer. But it makes some sense to me that PF and PK would work the same.

It looks like the 2e Phantasmal Force basically turned in to Major Illusion?

 

[Lanefan]

Phantasmal force has always worked that way, no?

Ah no, sorry, I'm confusing it with Phantasmal Killer. But it makes some sense to me that PF and PK would work the same.

It looks like the 2e Phantasmal Force basically turned in to Major Illusion?

2e PF (the 1st-level spell) turned into Minor Image in 3e. 2e Improved Phantasmal Force (the 2nd-level spell) turned into Major Image. Major Illusion sounds more like IPF or even Spectral Force (3rd-level spell).

Phantasmal Killer has always been a corner case looking for places to happen.

Lanefan

 

[Lidgar]

Agree that using it to create something the affected creature is either expecting or not out of the ordinary is typically the best use of it, if anything to avoid or delay the investigation check. That could be a hostile creature, large pit, noxious gasses, a strong wind, etc. In general, it has more utility to distract or delay the affected creature versus incapacitating or damaging it, but of course depends on the circumstances.

 

[lkwpeter]

Thanks for your answers!

1. Yes, the phantasm can move around with the target and take up its line of sight since it's in the target's mind. SAGE ADVICE

2. The phantasm can act as you "pre-program" it to do so, including attacking the target (specific damage in the spell's description), but it's going to be based off of YOUR memories/imagination of what it's supposed to look or sound like. Only the target can perceive it, you can't change it after casting.
SAGE ADVICE

3. Your caster can't accurately make something if he/she has no idea what it could look like, like the starship Enterprise for example, or the target's mother whom you've never met before.

4.) Could I cast an illusion of a city guard lieutenant that asks his subordinate to follow him somewhere?

5.) Am I right, that in contrast to other illusion spells the hostile creature does NOT recognize it as an illusion, after it interacted with it physically? That is only possible via an intelligence check, right?

6.) What spell do you think is more useful/powerful? Phantasmal Force or Suggestion?

 

[jaelis]

4.) Could I cast an illusion of a city guard lieutenant that asks his subordinate to follow him somewhere?

I don't think you have very fine control over what the illusion does, but I would let you set general parameters, like "I create an illusion of the lieutenent who orders the guard to report to the king." You would need to have seen the lieutenant.

5.) Am I right, that in contrast to other illusion spells the hostile creature does NOT recognize it as an illusion, after it interacted with it physically? That is only possible via an intelligence check, right?

That's right. That's what makes it awesome.

6.) What spell do you think is more useful/powerful? Phantasmal Force or Suggestion?

If I had to pick one I'd probably go with PF. In part because it isn't language dependent. But PF is also more DM dependent, so that's a factor.