Can Minor Illusion/Silent Image be used to make it look like you're about to cast other spells, to waste enemy Counterspells or Dispels?

Question

Can the "Minor Illusion" cantrip or "Silent Image" spell be used to emulate the casting of other spells?

Thus hopefully tricking another spell caster into wasting a 3rd lvl or higher spell slot to cast "Counterspell" or "Dispel"?

If you have played any spellcaster capable of casting Counterspell you know every time someone announces what spell they are casting like a well placed "Fireball" you or your foe jumps right up screaming "Counterspell". So far I have seen no one describe the visual appearance of the casting of a spell any spell other than a DM before/after announcing the spell´s name and level.

I'm specifically thinking of using the cantrip to emulate the casting of a different spell, not the effect. Just enough of a deception attempt to look like a spell is starting to complete casting, to make another spellcaster react.

Intended Examples:

• A ball of fire to emulate Fireball or a similar imagery like a bright glow at the tip of the PCs pointing finger to emulate the casting of said spell or even "Delayed Fireblast Fireball".

• Covering yourself in illusory flames to emulate "Investiture of Flame".

• Making your hand glow brightly to emulate "Sunbeam".

• A levitating disk of light to emulate "Portal"

I expect that in most of these cases an opposed or contested ability check would be required from one or both spell casters.

At a 60ft distance (maximum range for Counterspell) you would not hear the verbal incantations nor see the somatic movements very clearly if at all. So, the best indication would be any visible change like a glowing hand or finger. "Minor Illusion" only has a Vocal and a Material (a bit of fleece). "Fireball" (for example) has a Vocal (that would not be easy to heard), the Material (tiny ball of sulfur or bat guano) would be in your closed hand/fist (unable to be seen), and the Somatic component could be made mockingly or completely improvised. So, by making your finger glow, you could fool another spellcaster into thinking you are casting "Fireball".

Answer 1

Better way: simply just pretend to cast the spell

Before I get into answering your question as asked (and explaining why it won't work the way you want it to) let me propose a simpler, easier and less costly way of doing the same thing:

All you have to do is pretend to cast a spell while not actually casting anything. Take out components, do hand gestures, and start chanting but do not actually initiate the casting of any spell.

If you do that, and successfully trick a spellcaster into casting counterspell (or dispel) then you have made them waste a 3rd or higher level spell by expending no resources.

See this question for more on this.

No, incomplete spells do not have visual effects, so there is nothing to create an illusion of

Spells do not have any effects (visual or otherwise) until their casting is complete

You say:

So far I have seen no one describe the visual appearance of the casting of a spell any spell other than a DM before/after announcing the spell´s name and level.

And there is good reason for that.

To be perceptible, the casting of a spell must involve a verbal, somatic, or material component. [...]

If the need for a spell’s components has been removed by a special ability, such as the sorcerer’s Subtle Spell feature or the Innate Spellcasting trait possessed by many creatures, the casting of the spell is imperceptible. (XGtE)

This means that casting a spell has absolutely no observable effects outside of the verbal and somatic components as well as the handling of the material components. The effects of the spell only occur when the spell casting has been completed.

This is also supported by Jeremy Crawford:

Do you notice a spell being cast? The answer is based on whether you noticed any of the spellcasting components: V, S, or M.

Fireball as an example

Take Fireball for example. It has (as you mention) verbal, somatic, and material components.

Here is how the book describes the casting of Fireball:

Clad in the silver robes that denote her station, an elf closes her eyes to shut out the distractions of the battlefield and begins her quiet chant. Fingers weaving in front of her, she completes her spell and launches a tiny bead of fire toward the enemy ranks, where it erupts into a conflagration that engulfs the soldiers.

Note the lack of any discernible magic until the spell is completed.

The wizard uses verbal and somatic components ("begins her quiet chant. Fingers weaving in front of her..."), then completes the spell resulting in the effect ("launches a tiny bead of fire toward the enemy ranks").

Counterspell can only be used before a spell is complete

Counterspell says:

You attempt to interrupt a creature in the process of casting a spell.

In the example above, you can only cast Counterspell at the point at which the wizard is muttering and making hand gestures. Once they complete those and "a bright streak flashes from [their] pointing finger" it is too late to Counterspell because the casting has already been completed.

How trying to deceive using any illusion spell would work in practice

Let's say for this example there are two spellcasters: you and your opponent. You can both see and hear each other and you suspect that the next spell you cast your enemy will try to Counterspell. So you decide to try to trick them using Minor Illusion to emulate a Fireball spell.

Case 1: Counterspell right away

You start casting Minor Illusion by making gestures and holding material components. Seeing that you are starting to cast a spell, the enemy right away casts Counterspell and succeeds. Thus your Minor Illusion never completes but you have successfully made them "waste" a Counterspell.

Case 2: Chooses not to Counterspell

You start casting Minor Illusion by making gestures and holding material components. However, your opponent decides to not use Counterspell this time. Maybe they don't even hear or see you start to cast the spell, maybe they are low on slots and decide not to risk it. Either way, they decide not to cast Counterspell.

Thus, your Minor Illusion spell completes. You choose to have it create the effect "a bright streak flashes from your pointing finger". Your opponent sees this and may think for a moment that they have made a mistake and might be tricked into thinking you have cast Fireball. However, at this point, there is no way for them to actually Counterspell you. Your spell has completed and taken its effect and the spellcaster will soon realize that no Fireball is actually coming.

Results

Case 1 actually does exactly what you want it to (make them waste a Counterspell), but it can be done with literally any spell. Unless the wizard has a friend who is good at identifying spells they are not going to be able to identify what you are casting in time to see that the spell is not worth dispelling.

Case 2 does what you think you are attempting to try to make work, but no Counterspell is used. By the time they see your illusionary trick, it is too late to Counterspell it. Thus, defeating the whole purpose of the trick in the first place.

Your characters don't know what spells are being cast

You say:

every time someone announces what spell they are casting like a well placed "Fireball" you or your foe jumps right up screaming "Counter Spell"

However, it is important to note that even if you say "I cast minor illusion", the enemy does not automatically know that. That is why case 1 of my example worked.

Allowing you to know what spell an enemy is casting (or vice-versa) just because the name of the spell is announced at the table is metagaming and not the intended way for spells to function.

What you and your DM have to do is make sure that you are keeping player and character knowledge separate. If you do that, then I think you will find that Counterspell becomes much trickier to use. For one thing, they won't always be able to jump on the big damage spells but might accidentally catch you when you are casting a smaller spell or cantrip.

Most of what you want could not be made with Minor Illusion or Silent Image regardless

Minor Illusion's description limits its usage to either a sound (or series of sounds), or an image of an object (nothing else):

You create a sound or an image of an object within range that lasts for the duration. [...] The image can’t create sound, light, smell, or any other sensory effect.

So it would not be able to create:

a bright glow at the tip of the PC's pointing finger

Or any of these:

Covering yourself in illusory flames to emulate "Investiture of Flame".

Making your hand glow brightly to emulate "Sunbeam".

A levitating disk of light to emulate "Portal"

The description of Silent Image (which can be of "an object, a creature, or some other visible phenomenon") similarly states:

The image is purely visual; it isn't accompanied by sound, smell, or other sensory effects.

Minor Illusion also cannot create any type of movement.

Answer 2

No

Counterspell is used in reaction to the casting, not the effect of the casting.

So in this case, at the time Counterspell was used there would be no illusion created (By the time the spell effect shows up Counterspell is too late). The opponent would only have your words and actions to use to interpret what spell is being cast, and those words and actions would be from the illusion spell.

The action economy

There is a rule in XGE that says spell identification takes a reaction, so no single caster can both identify a spell and cast Counterspell in the same turn.

Personal feelings about that being ridiculous aside, that means two people are needed.

Scenario 1

1. Leon Hexblade starts casting minor illusion
2. John McSpellIdentifier checks to see what spell is being cast. Importantly he does this before any of the spell effects are activated, so just going from the V,S and M components.
3. John identifies the spell and yells to Sarah MsCounterspell that it is just a minor illusion spell

Scenario 2

1. Leon Hexblade starts casting minor illusion
2. John McSpellIdentifier checks to see what spell is being cast. Importantly he does this before any of the spell effects are activated, so just going from the V,S and M components.
3. John fails to identifie the spell and yells to Sarah MsCounterspell that he doesn't know. At this point Sarah has to decide if it is worth casting Counterspell based on no real knowledge

Scenario 2 is the only way a Counterspell can really be 'tricked'.

In neither scenario does the spell cast by Leon make any difference (Other than to the DC of the identification check), at the time of the identification and the Counterspell there is no effect from the spell, it is still in the process of being cast. It makes no difference if the minor illusion could look exactly like a fireball because it doesn't exist at the point in time of the Counterspell decision.

Counterspell

You attempt to interrupt a creature in the process of casting a spell.

Emphasis mine.

Answer 3

The effects you describe are within the capabilites of those spells.

Xanathars Guide contains optional rules about recognising spells as they are cast. An enemy would have to burn their reaction to make a fairly hard Arcana check to do it (the DC depends on the level of the spell cast). If they have only one spellcaster, this would mean that in most cases they will not be able to use counterspell or shield if they attempt it, and will have to react to your spell "blindly". This is true of any spell, though, so whether casting an illusion spell in a specific way could mislead them is up to the DM.

If you create a lasting effect, the illusion spells already mention how someone can discern their nature: they need to make an Investigation check versus your spell DC. As always, the DM can impose (dis)advantage on the check according to the circumstances. Someone who has never seen the spell you "emulate" might have disadvantage if the spell effect is obviously magical, but they are also unaware of its capabilities, so the usefulness of the illusion might also be limited. Someone who knows the spell might get advantage on the check or might know a way to succeed automatically by interacting with the image in some cases. This will depend on your DM. If you wish to employ this tactic, consult with them to make sure what you can expect of it.

Answer 4

Counter Spell? Sort of. Dispel Magic? Yes.

If they try to Counter Spell your illusion as you are casting it I would consider that a waste so yes in that sense, but once the illusion is cast counter spell will have no effect on it. You would need Dispel Magic to get rid of the Illusion. Which depending on the illusion your enemy may want to cast dispel on it.

I think a better question may be "Could I use a deception check to imitate spell casting?"

Answer 5

Yes, it can.

I think it's clever, and I would allow it. By this I mean silent image. As per the Sage Advice Compendium (emphasis mine):

The easiest way to stop a spell is to cast counterspell on its caster while it’s being cast.

There are more references to counterspell in that Sage Advice document, so check it out and do a search on "counterspell". All will be revealed.

Remember, the enemy mage must only think you're casting a spell, and they need not know which spell it is. From their perspective, they're seeing a Sorcerer casting some spell using subtle spell so that there is no verbal component.

With all due respect to other commenters (honestly), the spirit of D&D is in promoting out-of-the-box thinking and an entertaining narrative. Anyone unconvinced of this should watch the Acquisitions Incorporated sessions, DM'd by Chris Perkins.

What I would allow: just the image of a person gesturing -- forget about the nascent fireball, portal, etc. Also keep in mind that your illusionary mage is going to be walking from point A to point B; if someone notices this and sees through the illusion, then it fails. Lastly, there's no certainty that the enemy caster will take the bait and cast counterspell, so I'd have some kind of roll for that. But I would certainly let you do it.

My guiding principle is as mentioned in Save My Game, under the heading "Reward Creativity":

Many players of spellcasters don't bother casting spells that require creativity because DMs rob them rather than reward them when they try to be creative. The DM comes up with all kinds of reasons why the spell must adhere to a strictly limited effect. I'm not saying that 1st-level (or any level) enchantments and illusions should be all-powerful and able to do anything, or that you shouldn't be wary of overly clever players trying to exploit loopholes or push beyond what should be possible -- but if you want creativity, you need to reward it.

If you like a game that rewards creativity, play with players who enjoy this aspect of D&D.