[5E] Interrupting a Spellcaster via Ready Action

Nickolaidas

Explorer
Initiative Order:

1. PC Fighter
2. Grimlock
3. PC Wizard
4. Mind Flayer Arcanist
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"DM: PC Fighter, what do you do?

PC Fighter: I grab my spear and ready the following action: The second I see the Mind Flayer Arcanist attempting to cast a spell (using Verbal or Somatic Components), I throw my spear at the Mind Flayer's chest.

Grimlock: The monster dashes towards the PC Wizard and ends its movement right in front of him.

PC Wizard: I cast shield on myself.

DM: Magical energies surround you and you can feel more protected against enemy attacks. The Mind Flayer Arcanist moves its hands and makes hissing sounds as it is about to cast a spell …."
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Alright, so now what?

I've checked a few websites which talk about this, and there are quite a few opinions:

A) Some think that the Mind Flayer must FIRST cast the spell, and THEN the fighter throws his spear.

B) Others say that the fighter must FIRST throw the spear and THEN the Mind Flayer (if still alive) casts the spell.

Others say that in case of B):
1] If hit, the Mind Flayer must make a Concentration check or lose the spell …

or 2] If hit, the Mind Flayer must ONLY make a Concentration check if he was casting a spell which requires concentration to maintain.

Personally, I'm on camp B) and 2], but I want to hear your opinions as well. Do you fall under any of those categories? Or do you do something else entirely in situations like this?

I chose B) instead of A) because in case A), there's no reason for the PC Fighter to ready that particular action since he ALREADY plays BEFORE the Flayer via initiative and basically by choosing A) the Fighter allows the Mind Flayer to cast first and get hit second, instead of being hit on the Fighter's turn and if killed, never casting a spell in the first place.

Now I chose 2] instead of 1], because a caster ALWAYS rolling for concentration check any time he gets hit via Ready Action risks me rendering a caster useless. All I have to do is having 2-3 fodder monsters ready their action to hit a PC Caster anytime he's about to cast a spell and every single round the caster may have to roll THREE concentration checks or never actually manage to cast the simplest of cantrips. Option 2] on the other hand can be better because the caster can still cast basic spells without running the risk of losing them, and the risk of being KO'd before casting still exists.

Thoughts?
 
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dnd4vr

Keeper of the Seven Keys
So 2B or not 2B? That is the question??? ;)

Seriously though, I mostly agree with your take on it and that is how we play, except was play with [1], casters hit by readied actions must always make a Concentration check or the spell is ruined. It makes casting harder, but otherwise it is too powerful IMO.

. I don't recall anything in the rules about it, but since the readied action was about the instant the Mind Flayer shows signs of casting, etc. However, I would also have the PC Fighter have to recognize the spell as such. The Mind Flayer, seeing the PC Fighter waiting, could just wave his hands and make squishy-gurgling noises, the spear is thrown, and then actually casts the spell.
 
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MarkB

Hero
It's pretty simple. "You can take your action right after the trigger finishes." If the trigger is someone casting a spell, you take your action after they cast the spell.
 

dnd4vr

Keeper of the Seven Keys
It's pretty simple. "You can take your action right after the trigger finishes." If the trigger is someone casting a spell, you take your action after they cast the spell.
But that wasn't the triggering event, the triggering event was the Mind Flayer moving or "speaking" (somatic or verbal) while casting its spell. I understand your point, but 5E has really made it very difficult for spells to not be disrupted during the casting process since most are casting times of simply 1 action.
 

Nickolaidas

Explorer
It's pretty simple. "You can take your action right after the trigger finishes." If the trigger is someone casting a spell, you take your action after they cast the spell.
So basically the only reason a PC would ready an action to hit a spellcaster is to break his concentration IN CASE he casts a spell with ongoing duration.
 

MarkB

Hero
But that wasn't the triggering event, the triggering event was the Mind Flayer moving or "speaking" (somatic or verbal) while casting its spell.
And when does it finish moving its hands and speaking its verbal components? After it finishes casting.
 

MarkB

Hero
So basically the only reason a PC would ready an action to hit a spellcaster is to break his concentration IN CASE he casts a spell with ongoing duration.
Pretty much. The Ready action's utility was significantly reduced in 5e, with the only major compensation being that it doesn't change your initiative position anymore (so, in the OP's example, if the Fighter attacks the Mind Flayer with his readied action, he'll then be able to take his turn immediately afterwards, before the Grimlock, rather than having to wait until just before the Mind Flayer's next turn).
 

Nickolaidas

Explorer
The way I see it, an attack used as a readied action - which is used as a reaction, acts like the counterspell (which is ALSO a reaction) - it is done before the spell (which is counterspelled) can have any effect.

However, while counterspell is a sure thing (unless the spell is quite a few lvls above its league), the physical attack only does damage and can only prevent the spell in case it kills the spellcaster or if the spellcaster casts a concentration spell AND fails the concentration check … so I don't think that physical attacks used as readied actions to hit a spellcaster run the risk of rendering counterspell or spellcasting useless.
 

Nickolaidas

Explorer
Pretty much. The Ready action's utility was significantly reduced in 5e, with the only major compensation being that it doesn't change your initiative position anymore (so, in the OP's example, if the Fighter attacks the Mind Flayer with his readied action, he'll then be able to take his turn immediately afterwards, before the Grimlock, rather than having to wait until just before the Mind Flayer's next turn).
Thanks for the feedback! You too, dnd4vr!
 

DM Dave1

Adventurer
And when does it finish moving its hands and speaking its verbal components? After it finishes casting.
But finishing the spell need not be the trigger for the Readied Action.

PC Fighter: if the Flayer starts moving its hands or speaking words to cast a spell, I spear it.
 
I can see it going either way and as a player wouldn't really care what the DM decided.
As a DM, I'd probably allow a readied action to force a concentration check to continue casting the spell. If it becomes a usual thing, I can just have the caster not cast a spell or get to a position where they can't see it start casting. There are ways to really make it a choice to give up a full attack action or just risking a single attack that could be wasted if they can't see the enemy start casting.
 

dnd4vr

Keeper of the Seven Keys
But finishing the spell need not be the trigger for the Readied Action.

PC Fighter: if the Flayer starts moving its hands or speaking words to cast a spell, I spear it.
Precisely. The condition that triggers the readied action need not mean the action it was part of "finished" as well. That is pretty much up to the DM's discretion/interpretation. Because casting times are so quick in 5E, a readied action is the only way to possibly stop it. It is just one of the ways our group prefers older initiative systems.

Alternatively, you could rule that any attack on the Mind Flayer prior to it going that hits could disrupt the spell before it is cast if he fails a concentration check, but that really only works reasonably well if you don't use the roll-and-repeat standard initiative rules. If you use those, it is great if the player caster rolls high because his spells can't be stopped but sucks if he is last and every attack has a chance of ruining his spell.

In short, there are many ways you can handle this. Find what works best for your group and enjoy! :)
 

MarkB

Hero
But finishing the spell need not be the trigger for the Readied Action.

PC Fighter: if the Flayer starts moving its hands or speaking words to cast a spell, I spear it.
That just opens up more room for disagreements. If the Mind Flayer hasn't actually cast the spell yet, how do you know that's what it's doing, as opposed to speaking or gesturing to an ally? Must the Fighter take his readied action the moment the Mind Flayer utters any word or makes any gesture?

And again, you take your readied action after the trigger finishes. What counts as someone finishing starting moving their hands or speaking words?
 

dnd4vr

Keeper of the Seven Keys
That just opens up more room for disagreements. If the Mind Flayer hasn't actually cast the spell yet, how do you know that's what it's doing, as opposed to speaking or gesturing to an ally? Must the Fighter take his readied action the moment the Mind Flayer utters any word or makes any gesture?

And again, you take your readied action after the trigger finishes. What counts as someone finishing starting moving their hands or speaking words?
You know he is casting a spell by making an Intelligence (Arcana) check with DC 15 + spell level being cast (XGtE, p. 85). The DM could have told the PC Fighter player, "You see the Mind Flayer start to move its hands and gurgling, roll an arcana check." If the character fails the check, maybe he doesn't recognize the spell as such before the Mind Flayer finishes it? Or the player could just say he throws the spear immediately, risking his throw in case the Mind Flayer was, indeed, faking it.

What I don't like about the lack of casting times in the old sense is it is very hard to stop an enemy caster from using magic unless you are a spellcaster yourself with Counterspell (which Clerics and Druids don't get...).

But I agree it can be open to interpretation so I just let the DM adjudicate it as they see fit.
 

dnd4vr

Keeper of the Seven Keys
Which costs you your reaction, leaving you none with which to take your Readied action.
The rule I stated was for determining the exact spell being cast. The DM could just as easily rule it as Insight check or similar against the Mind Flayer's Deception (if it was actually trying to fool the PC Fighter). Of course, with that thinking the Deception act by the Mind Flayer could constitute its action! LOL

And as I wrote in my post, the player could simple react and throw the spear immediately, without deciding to make the check. Again, lots of ways to handle this.
 

dnd4vr

Keeper of the Seven Keys
That’s interesting. Is that written somewhere? I’ve not heard that rule but I like it.

The rule to make the Arcana check does use your reaction. Since the readied action allows you to use your reaction in response to the trigger, if you make the Arcana check you have no reaction remaining to act when the readied action is triggered.
 

DM Dave1

Adventurer
That just opens up more room for disagreements. If the Mind Flayer hasn't actually cast the spell yet, how do you know that's what it's doing, as opposed to speaking or gesturing to an ally? Must the Fighter take his readied action the moment the Mind Flayer utters any word or makes any gesture?

And again, you take your readied action after the trigger finishes. What counts as someone finishing starting moving their hands or speaking words?
Simple: There should be no disagreement because the DM makes a ruling, like [MENTION=6987520]dnd4vr[/MENTION] stated above. I would say the trigger is finished as soon as the Flayer starts moving its hands or starts to speak in a spell-like fashion, just as the player intended. Then it's up to the player to decide for their PC if they think it is a spell or not. If the player then says their PC tries to recognize the Flayer's motion (or speech) as spellcasting before throwing the spear, the DM might call for an Arcana roll. If the player rolls well, the PC is pretty sure it's a spell (or not). If they roll poorly, they have no idea. In any case, the player gets to decide if the PC carries out the action, or ignores the trigger, per the rules of the Ready action.

How about another example. Let's say the fighter readied this action: "I throw my spear at the Flayer if it starts moving towards us". As a DM, would you really insist the the Flayer finish its movement - perhaps it moves 20' to get next to the wizard, attacks, then moves its last 10' to get next to the fighter - before allowing the fighter to throw the spear? I think this case is very clear: the trigger finishes as soon as the Flayer takes one step closer and the fighter can throw the spear or ignore the trigger, per the rules.
 

MarkB

Hero
The rule I stated was for determining the exact spell being cast. The DM could just as easily rule it as Insight check or similar against the Mind Flayer's Deception (if it was actually trying to fool the PC Fighter). Of course, with that thinking the Deception act by the Mind Flayer could constitute its action! LOL

And as I wrote in my post, the player could simple react and throw the spear immediately, without deciding to make the check. Again, lots of ways to handle this.
Which still doesn't address the second part of my post. Readied actions, unlike reactions in general, don't occur immediately. They happen after the trigger finishes. That leaves a lot less room for interpretations that allow an action to be interrupted.

That’s interesting. Is that written somewhere? I’ve not heard that rule but I like it.
It's the rule [MENTION=6987520]dnd4vr[/MENTION] was referencing - Xanathar's, page 85.
 

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