D&D 5E Invisibility, non-instantaneous spells, and spell effects

Irlo

Adventurer
Disclaimer: What follows, sparked by the comment quoted below from another thread, is meant to be a good-natured digression and exploration of spell mechanics and is not intended to challenge anyone's interpretation of RAW. It's ridiculously pedantic and should be taken in that spirit.

EDIT: I'm a DM. I know what my ruling would be. This is a theoretical discussion about how folks on the forum interpret spell mechanics. Thanks!

Things that are instantaneous are labeled as such.

The spell invisibility is not instantaneous in duration, nor are the spell effects specified to be instant. Can I cast a readied magic missile to use when the target begins to turn invisible? Why or why not?

YES. It takes only a fraction of a second to use a spell as a reaction. The invisibility spell does not specifically state that the invisible condition is applied instantly, so there is some small but perceptible duration of time after completion of spell that the target is visible and fading away. Plus, I like the idea of a quick but gradual fade-away as the magic kicks in.

NO. The magic missile spell is only valid on a target that the caster can see. Spell effects occur instantly upon competion of the spell unless stated otherwise, and don't require an instantaneous label or descriptor to be instantaneous. [Is there a rule to that effect, or is it just a reasonable ruling on the part of the DM?]
 
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Hand of Evil

Adventurer
Epic
What does your GM say, they have the final say no matter what is debated here? It is based on the Initiative.

Now, you have every situation to think about.
 

payn

Legend
I'm assuming combat has already begun and a caster has used the ready action to prepare magic missile.
In that case, I dont typically allow this level of granularity of ready action. They either blast them with missile before, or the target goes invisible, they dont happen simultaneously.
 

Cruentus

Adventurer
I would have the player who is readying identify when they will cast magic missile:

1) When an enemy begins to cast a spell? (Any enemy, the first enemy?) - ok.
2) When an enemy goes invisible? For me, that's not a sufficient trigger. What happens if they Misty Step? It looks like invisibility when they vanish, for example.

The player also wouldn't be able to know if the enemy was casting Invisibility anyway, so that wouldn't be a trigger either, at least in my interpretation.
 

I’d allow you to hit them as they cast. As they dance their jig and as they are verbalizing those invisibility adjectives. And, finally, the moment you see that gum arabic, you’re like, “THIS IS IT!”

You let those missiles fly. He completes the spell and turns invisible but it’s too late because those darts of force are already en route, homing in on the intended target. Make a concentration check, bub.
 

James Gasik

Legend
Supporter
The Ready rules say you can respond to a particular, perceivable circumstance. But that the action goes off after the trigger. If the trigger is "the enemy becomes invisible", it comes down to the DM's interpretation of whether you vanish all at once or fade from view gradually.

I think most tables would run it as an instant "Ninja vanish!" and thus you can't react to the trigger, because after the trigger has resolved, magic missile no longer has a legal target.

If, however, you readied against casting a spell, that certainly works because you have to complete the components of the spellcasting- even if they don't require a lot of fanfare, it takes at least some time to shake your arcane focus and shout "Evanesco" (or whatever the kids are saying these days).
 

Dausuul

Legend
My ruling would be no. A readied action happens immediately after the triggering event unless otherwise stated; you can't get around that by saying "I ready for when [triggering event] begins to happen."

In general, I'd say by the time you see your opponent start an action, you've lost your chance to pre-empt it with a readied response. Once they start, you can't respond till they finish.

The exception would be if the action has discrete pieces such that the person acting can do other things (e.g., move) in between. So you could ready for an enemy's attack, and you'd go after their first attack but before the second. But you can't ready for when they "start to attack"--they always get the first swing.
 
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James Gasik

Legend
Supporter
The ready rules don't say anything about responding to actions, just responding to triggers, "a particular, perceivable circumstance". Could I not ready to act when an archer draws back their bow, and then have my readied action trigger before they loose the arrow?
 

What does your GM say, they have the final say no matter what is debated here? It is based on the Initiative.

Now, you have every situation to think about.
Really wish more folks would consider the option of "this person IS the DM, and is looking for analysis or advice." Because I swear, this response comes up in the first 5-10 posts of every single thread ever about any rules question, and at least half the time, it's a DM wanting other DMs' thoughts to help guide their choice, making this response less than useless.

As for my own perspective:

If the player who readied the magic missile (or some other instant-cast spell) set an appropriate trigger, I'd allow it. E.g., "I ready magic missile for when the other character casts a spell" or "attempts to turn invisibile" or the like. However, you can't have it "both ways" as it were, in terms of affecting the target--you don't get to say that the spell hasn't taken effect yet so you're allowed to hit it, but has taken effect so you can force a Concentration save. One or the other: either the spell isn't up yet, so you're able to target the creature (but the creature isn't Concentrating yet), or the spell is up and you're having to deal with the "you don't know where it is" problem.
 

el-remmen

Moderator Emeritus
I was going to respond, but then realized my response was based on my table's grandfathering the ready/delay rules from 3E.
 

Dausuul

Legend
The ready rules don't say anything about responding to actions, just responding to triggers, "a particular, perceivable circumstance". Could I not ready to act when an archer draws back their bow, and then have my readied action trigger before they loose the arrow?
My problem with this is that it effectively nullifies the statement that the readied action comes after the trigger. "When the archer draws their bow" is very obviously an attempt to react to the archer's attack; but the player is trying to split hairs so they get to go before the attack actually happens. You can almost always find a way to split that hair fine enough if you try, and I have no desire to get into that.

Treating the action as an atomic whole allows me as DM to draw a clear line which doesn't invite endless debate: Once an action starts, it can no longer be stopped (unless you have a special reaction like counterspell that specifically interrupts other actions). You have to decide which is more important to you, knowing the enemy's plan or striking first.
 
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Child#5118

Villager
Disclaimer: What follows, sparked by the comment quoted below from another thread, is meant to be a good-natured digression and exploration of spell mechanics and is not intended to challenge anyone's interpretation of RAW. It's ridiculously pedantic and should be taken in that spirit.

EDIT: I'm a DM. I know what my ruling would be. This is a theoretical discussion about how folks on the forum interpret spell mechanics. Thanks!



The spell invisibility is not instantaneous in duration, nor are the spell effects specified to be instant. Can I cast a readied magic missile to use when the target begins to turn invisible? Why or why not?

YES. It takes only a fraction of a second to use a spell as a reaction. The invisibility spell does not specifically state that the invisible condition is applied instantly, so there is some small but perceptible duration of time after completion of spell that the target is visible and fading away. Plus, I like the idea of a quick but gradual fade-away as the magic kicks in.

NO. The magic missile spell is only valid on a target that the caster can see. Spell effects occur instantly upon competion of the spell unless stated otherwise, and don't require an instantaneous label or descriptor to be instantaneous. [Is there a rule to that effect, or is it just a reasonable ruling on the part of the DM?]
Just ask your GM about.
 

My problem with this is that it effectively nullifies the statement that the readied action comes after the trigger. "When the archer draws their bow" is very obviously an attempt to react to the archer's attack; but the player is trying to split hairs so they get to go before the attack actually happens. You can almost always find a way to split that hair fine enough if you try, and I have no desire to get into that.

Treating the action as an atomic whole allows me as DM to draw a clear line, which is easy for everyone to understand: Once an action starts, it can no longer be stopped (unless you have a special reaction like counterspell that specifically interrupts other actions). You have to decide which is more important to you, knowing the enemy's plan or striking first.

Of course, DM discretion needs to be taken into account and methinks your atomic whole is more molecular, IMO. Just because an enemy draws their bow does not mean they are going to fire. I mean, they probably are, but that gesture could be part of a creative intimidation attempt rather than an attack. I personally see no problem with "drawing the bow" being a trigger. The hair is not too fine in this instance for my DM ruling. What if the archer has multi-attack or Extra Attack? Would you be okay with the trigger being in-between the attacks? Or, because the multiple attacks are all part of an Attack Action, the full attack must be resolved in order to activate the trigger?

Let's look at another combat scenario: Would you rule that the goblin must complete its full movement forward before the rogue can throw a dagger at it when the Ready was stated as: "If the goblin steps toward us, I will throw my dagger at it"? Is the hair too fine here or must we wait for the goblin to use its full 30' of movement?

Of course, DM discretion needs to be taken into account and you are within your right to determine the size of the atoms at your table.


As for the OP, the trigger would necessarily have to be the casting of the spell and not the spell effect. YES, this works: "If Kaloruk sees the mage start casting a spell, he'll unleash Magic Missile on him." NO, the mage is already invisible and spell slot is wasted: "If Kaloruk sees the mage going invisible, he'll unleash Magic Missile on him."
 

the Jester

Legend
No way. A reaction occurs after the trigger. At no point does invisibility say that the target takes any time to turn invisible. You cast and then the target is invisible, poof, almost, ahem, almost like magic. It's too late to target them unless you can see invisible creatures.

If you ready an action to magic missile some guy if he casts a spell, you don't interrupt his spellcasting.
 

Dausuul

Legend
What if the archer has multi-attack or Extra Attack? Would you be okay with the trigger being in-between the attacks? Or, because the multiple attacks are all part of an Attack Action, the full attack must be resolved in order to activate the trigger?
I'll quote my original post on the subject:

"The exception would be if the action has discrete pieces such that the person acting can do other things (e.g., move) in between. So you could ready for an enemy's attack, and you'd go after their first attack but before the second. But you can't ready for when they 'start to attack'--they always get the first swing."

Let's look at another combat scenario: Would you rule that the goblin must complete its full movement forward before the rogue can throw a dagger at it when the Ready was stated as: "If the goblin steps toward us, I will throw my dagger at it"? Is the hair too fine here or must we wait for the goblin to use its full 30' of movement?
Movement isn't an action. And if it were, the principle above would apply. You can break your movement into pieces and do other stuff in between; therefore, your opponents can also do stuff in between.

If it ever became an issue, I'd probably use "5 feet" as the cutoff: That's how far the enemy can move before you get to respond.
 

BookTenTiger

He / Him
I usually rule in favor of the characters and what would make for a cool narrative.

A spellcaster firing off some magic missiles right as an enemy starts to turn invisible is fun, cinematic, and definitely not game breaking.

So I'd allow it!
 

I'll quote my original post on the subject:

"The exception would be if the action has discrete pieces such that the person acting can do other things (e.g., move) in between. So you could ready for an enemy's attack, and you'd go after their first attack but before the second. But you can't ready for when they 'start to attack'--they always get the first swing."
Sheesh, you'd think I could scroll up or something. We're still on page 1 even. Sorry about that! :oops:

Movement isn't an action. And if it were, the principle above would apply. You can break your movement into pieces and do other stuff in between; therefore, your opponents can also do stuff in between.

If it ever became an issue, I'd probably use "5 feet" as the cutoff: That's how far the enemy can move before you get to respond.
Fair enough.
 

My justifying saying "no" to the above is that this is a turn-based game. We might be trying to model a simultaneus real-time event, but all the rules are turn based. Trying to do anything simultaneous and realtime breaks the rules very quickly. For example, the issues in this thread. :)

A triggers of "starts to attack" doesn't make sense in the rules. I'm not even sure they make sense in real life. I mean, in combat you are continually moving, raising and lowering your weapons and shield, ducking and weaving, feinting, drawing back, observing your target, moving to face them, and so on. At what discrete point are you not starting an attack?

A trigger of "starts to move" is even worse. At what point have they started to move? When they've moved a planck distance?
 

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