Use Magic Missile to determine whether a statue is an Object or a Creature?(!)

[Travis Henry]

Last night, I was DMing an old Basic D&D adventure, updated for 5E. And discovered a curious use of the Magic Missile spell.

The party had a tough fight with a Living Rock Statue, which they defeated, and then...around the next corner was another statue. They ran into the room, and a player asked "roll for Initiative?" I'm like: "Yes."
So they roll Init and I have them go, and they are all wailing on this statue, which hasn't even moved yet. The wizard tries to cast "Magic Missile." And I'm like..."For some reason, you're not able to target it." The spell isn't even cast. The player is spooked. He's thinking there's some sort of Anti-Magic field. And then, bottom of the order...it's the statue's turn.

But, it's just a statue.

I say: "Well, y'all pounded it. It's all bent of of shape. It's not moving. Apparently it never even had a chance to move."

And the party is so proud that they got the jump on this monster. High fives all around.

But...it was just a statue.

Then I realized that Magic Missile can be used as a utility spell to determine whether something that looks like an Object (such as a statue, icicle, or stalactite) is really just an Object or whether it's a Creature (a Golem, Living Statue, Animated Object, Ice Mephit, Gargoyle, Piercer, or Mimic). Is that y'all's understanding as well?

 

[iserith]

Then I realized that Magic Missile can be used as a utility spell to determine whether something that looks like an Object (such as a statue, icicle, or stalactite) is really just an Object or whether it's a Creature (a Golem, Living Statue, Animated Object, Ice Mephit, Gargoyle, Piercer, or Mimic). Is that y'all's understanding as well?

Yes, though arguably in a lot of these situations the creature might have False Appearance which makes it indistinguishable from an object. The DM could rule, based on that, that magic missile does not work while the creature meets the requirements for False Appearance (usually when it remains motionless). This makes it somewhat less reliable as a means to identify such creatures. Some DMs may also rule that the spell slot is spent even if it has no effect.

I think the chief issue in the above example though is calling for Initiative when this wasn't actually a clash between two or more sides in conflict. Essentially, you established by the call for initiative that the statue was a creature, only it was not. This isn't a judgment as to the outcome, which you say your players enjoyed, only that this might be something worth thinking about in future games.

 

[77IM]

A cheaper version is eldritch blast, a cantrip which only targets creatures.

I can't find anything in the rules that say what happens when you try to cast a spell at an invalid target. Some DMs may rule that the spell is still cast and appears normal, but does not create any effect, e.g. the magic missiles hit the object but deal no damage. Other DMs might rule that the spell has some alternate effect, like reduced damage, or that it requires an ability check to work properly.

 

[iserith]

I can't find anything in the rules that say what happens when you try to cast a spell at an invalid target.

Xanathar's Guide to Everything (p. 85-86): "If you cast a spell on someone or something that can't be affected by the spell, nothing happens to that target, but if you used a spell slot to cast the spell, the slot is still expended."

This section is presented as an expansion on the spellcasting rules in the PHB and DMG. If the DM isn't aware of it or the group doesn't use this book (or the relevant section thereof), then obviously it may not apply.

 

[ccs]

I think the chief issue in the above example though is calling for Initiative when this wasn't actually a clash between two or more sides in conflict. Essentially, you established by the call for initiative that the statue was a creature, only it was not.

Oh bull. It was merely determining in wich order the party was acting in. That can be important to know in more instances than just when there's a foe present.
And btw the OP didn't call for the initiative roll. The players asked & he just said Ok. So it was the players themselves sorting out what order they acted in.

 

[robus]

Oh bull. It was merely determining in wich order the party was acting in. That can be important to know in more instances than just when there's a foe present.
And btw the OP didn't call for the initiative roll. The players asked & he just said Ok. So it was the players themselves sorting out what order they acted in.

This is another reason for having initiative pre-rolled at the end of the previous encounter to avoid the combat swoosh mode change and attendant expectations. The DM could have have simply asked each player what they do in initiative order without calling for initiative.

 

[iserith]

Oh bull. It was merely determining in wich order the party was acting in. That can be important to know in more instances than just when there's a foe present.
And btw the OP didn't call for the initiative roll. The players asked & he just said Ok. So it was the players themselves sorting out what order they acted in.

According to the OP, the PCs had just fought a "living rock statue." They saw another statue. A player asked if they should roll initiative. The players' belief that the statue was more than it seemed may have been encouraged by the DM's assent.

"A typical combat encounter is a clash between two sides..." (PHB, p. 189)
"Initiative determines the order of turns during combat." (PHB, p. 189)

While it's fine to use initiative for other purposes, the players can be forgiven for thinking that this was the DM implying the statue was indeed a foe to be defeated in combat. So however this scene turned out (positively, according to the OP), it's a good meditation for DMs to consider what they say and how it could be interpreted by the players.

 

[Hawk Diesel]

I typically don't worry that much about the distinction between creature or object with regard to spells. How would a spell be able to determine that any better than the caster? It would be like saying a gun or a bullet knows whether it's being fired at a person or a wall. Or, for the sake of a D&D discussion, a bow or a sword knowing this.

Now, I can see a case being made for a gun/sword/bow having less effect. There might be only a scratch, for instance, if such weapons were used on a stone wall. But it doesn't stop them from being used.

I feel the same way about spells. It doesn't stop them from being used. A magic missile used on a section of stone wall may just mark the surface. But that alone doesn't tell you if the target was a creature.

But then, for example, if you cast charm person on someone, how do you know if it works? Do you get a mental ping that it was successful? I would posit that instead, you know it works when the person starts listening to you and treating you friendly. If you cast it on a statue, you would likewise know the spell didn't work not because of some intuition of success or failure, but rather because the statue doesn't change how it reacts to you. Then it's up to the player to decide if this is because it's a creature that saved, or is just not a creature.

 

[robus]

I typically don't worry that much about the distinction between creature or object with regard to spells. How would a spell be able to determine that any better than the caster? It would be like saying a gun or a bullet knows whether it's being fired at a person or a wall. Or, for the sake of a D&D discussion, a bow or a sword knowing this.

Magic missiles are much more like heat-seeking missiles though. They are self-guided, but only toward creatures. Given that the darts are created and then directed, if there were no creature targets, I imagine the darts would dance about for a bit and then fizzle out, costing the caster a spell slot.

 

[Hawk Diesel]

Magic missiles are much more like heat-seeking missiles though. They are self-guided, but only toward creatures. Given that the darts are created and then directed, if there were no creature targets, I imagine the darts would dance about for a bit and then fizzle out, costing the caster a spell slot.

Sure, but heat seeking missiles don't just plummet out of the sky when launched in the absence of targets without a sufficient heat signature. They can still be aimed at a target and destroy that target as intended. They just don't correct course without that thermal input (I imagine. I don't know much about military weaponry).

You can certainly make a case for magic missile behaving in this way. But for me, it is problematic because it requires a couple of assumptions:

1) There is a real and objective distinction between what is living and what is not.

2) The magic utilized by spellcasters is able to intuitively or automatically sense this objective trait.

3) If the distinction between living and not living is not objective, then the magic employed by a spellcaster is capable of making these judgments without input from the caster. Meaning magic has a sort of limited artificial intelligence.

For me in my games, these assumptions bother me. I typically like to play in worlds that are more subjective or relative as opposed to concrete and objective. Good and Evil are not clearly defined or objective realities, but rather very much exist in the greys that we know and understand. The difference between life and death, or at least life and not-life is likewise blurry and ill-defined.

In such a world, it doesn't make sense to have magic innately able to sense and thus define what is alive and what is not.