Psychic Blades from Illusionary Fog

Question

If attacking from an illusionary fog created by Silent Image using the Soulknife's Psychic Blades would that reveal the fog to be an illusion to onlookers?

Physical objects like an arrow or dagger coming from illusionary fog would reveal nature the illusion

If you pass through mist made by the silent image spell, you notice it's illusory because it doesn't respond to your passage naturally. #DnD

— Jeremy Crawford (@JeremyECrawford) October 26, 2016 https://x.com/JeremyECrawford/status/791378153390215169

However there is precedent for physical objects like an arrow or dagger coming from illusionary darkness not revealing the nature of the illusion

If a person walks into it, they can immediately see it's an illusion (it doesn't actually block light). Outside observers would still need to use their action to investigate as specified in the spell. Arrows passing through darkness isn't a giveaway. #WotCStaff

— Dan Dillon (@Dan_Dillon_1) November 13, 2019 https://x.com/Dan_Dillon_1/status/1194418637144121344

But Psychic Blades are a shimmering energy that disappears after hitting or missing

You can manifest your psionic power as shimmering blades of psychic energy. Whenever you take the Attack action, you can manifest a psychic blade from your free hand and make the attack with that blade. This magic blade is a simple melee weapon with the finesse and thrown properties. It has a normal range of 60 feet and no long range, and on a hit, it deals psychic damage equal to 1d6 plus the ability modifier you used for the attack roll. The blade vanishes immediately after it hits or misses its target, and it leaves no mark on its target if it deals damage.

How would this be ruled?

Answer 1

The DM will need to make a ruling

That is exactly what the DM is there for.

You ask:

If attacking from an illusionary fog created by Silent Image using the Soulknife's Psychic Blades would that reveal the fog to be an illusion to onlookers?

There's nothing in the description of the silent image spell or in the description of the Soulknife's psychic blades that gives a definitive answer.

The tweets from WoTC staff are interesting, but 1) they're not official, 2) they're mostly talking about someone walking into an illusion.

Dan Dillon's comment "Arrows passing through darkness isn't a giveaway" is interesting, but at best tangentially related.

How does the DM decide?

Since there's no clear answer, the DM will need to make a ruling. Some DMs may immediately say yes it does, or no it doesn't, depending on their own world, experience, and opinions of the game.

It's certainly significant that there's no reason to believe that a shimmering blade of psychic energy would disturb real fog. But that alone is unlikely to be the sole basis of the DM's judgment.

The DM might want to know any number of things:

• what does the illusionary fog look like
• did the fog just show up, out of nowhere
• what are other conditions (inside, outside, sunny, raining)
• do viewers have any other reasons to be skeptical
• how experienced the viewers are with fog, psychic blades, illusions

In other words, the ruling is highly dependent on the exact situation.

My own opinion, if it's a foggy morning, and a couple of nervous and inexperienced guards see a couple of shimmering blades of energy come out of a particularly thick patch of fog straight at them, they're unlikely to question it.

On the other hand, bright sunny day, a highly knowledgeable observer who knows they're facing adversaries who include a spellcaster, and maybe the blades are targeting someone else, much more likely to be skeptical.

From the player's point of view

If you actually want to execute this in a game

Consider talking to the DM about it out of session. Ask their opinion. They might have further insight as to how this will work in your particular game.

If this is a thought experiment

Think of it narratively. What story are you imagining? Put yourself in the position of the DM. How would you rule?