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This question is prompted by both Sage Advice and this similar Pathfinder question. Let's use the scenario from Sage Advice:

Can you cast a reaction spell on your turn?

You sure can!

Here’s a common way for it to happen: Cornelius the wizard is casting fireball on his turn, and his foe casts counterspell on him. Cornelius also has counterspell prepared, so he uses his reaction to cast it and break his foe’s counterspell before it can stop fireball.

In this case, it seems as though Cornelius would be casting 2 spells at the same time - Fireball; and (before Fireball is complete) Counterspell.


The order of events alluded to by Sage Advice would be:

  • Cornelius begins casting Fireball
  • Cornelius' opponent begins casting Counterspell
  • Cornelius casts Counterspell, preventing his opponent's spell
  • Cornelius finishes casting Fireball
  • There is much fire

So far as I've been able to tell, it seems that the example given in Sage Advice would result in Cornelius essentially casting Fireball and Counterspell simultaneously.

By extension of the same mechanic, a caster could cast Shield in response to an Opportunity Attack by an opponent with the Mage Slayer feat. A Warlock could use Hellish Rebuke in the same circumstance.

This doesn't seem correct, at first glance, as it means that a caster would be able to do multiple complex somatic components, or to incant arbitrarily many verbal components simultaneously.

This seems strange enough that it may be that the Sage Advice column has overlooked a rule preventing this. Alternatively, they may have just skipped an implicit "but you give up the fireball by doing this, of course".


In short, can a character effectively and successfully cast two spells at the same time?

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Yes, you can cast multiple spells at the same time and have both take effect

There are no rules against this

The rules are fairly clear about what is and is not allowed with regards to when and how spells can be cast. The restrictions on spellcasting timing come down to two major rule categories:

  • Action economy
  • Concentration

As long as you have the action available to cast the spell with all the appropriate rules that all spells must follow then you can cast it. There is no rule that restricts casting with respect to ongoing casting and certainly nothing that implies that it is in any way cancelled.

Sage Advice Compendium explicitly allows it and there appears to be no mistake

You quoted it and I understand being sceptical, but there is no reason to think that this is a mistake. It contradicts no rules and it is an official rules clarification document.

If counterspell did not work this way, there would be no way to counter a counterspell to one of your own spells. And the whole point of this Sage Advice was to clarify that counterspell is intended to allow this.

However, that is not the only example of casting spells at the same time.

Spells with casting times longer than 1 action/reaction is another place where this could happen

When you cast a spell with a casting time longer than a single action or reaction, you must spend your action each turn casting the spell, and you must maintain your concentration while you do so.

Take this case for example:

  • Cornelius begins casting simulacrum
  • Cornelius casts feather fall in response to someone falling
  • Cornelius continues casting simulacrum
  • After the casting time is completed, simulacrum takes effect

In this case, you do actually kind of cast two spells at the same time. And this should work with any type of spell cast as a reaction during the casting of a spell with a duration greater than 1 action or reaction. As long as the caster maintains concentration and uses their action every turn to continue casting the long spell, they can do whatever they want.

Note that this will not work with bonus action spells because the restriction on those means that only 1 action cantrips can be cast the same turn.

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    \$\begingroup\$ Why can you not use Bonus Actions spells with this? I assume you're saying maintaining the spell counts as casting it each turn? So then could, say, an abjuration wizard heal their ward several times with one spell? \$\endgroup\$ – Medix2 Jul 12 '18 at 1:42
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Simultaneously, No. In the same turn, Yes.

Sage Advice has already addressed the issue of casting multiple spells in the same turn, which is very much RAW.

But HOW this is physically possible with split-second type spells?

An important thing to remember is that a spell targeted with Counterspell has its spell slot spent, whether or not the spell is successfully countered.

But a spell slot is only spent after the spell would normally be successfully cast (based off of the fact that using faulty materials/gestures does not result in a wasted spell slot).

This would imply that Counterspell takes place AFTER the targeted spell has been cast (but before it outputs its effects). Holding your action for a reaction to grapple someone if they attempt to cast a spell may stop them from casting a spell, but this does not make them waste the spell slot.

However, it is possible to "hold" a spell after the casting time is finished to use as a reaction, and thus possible to interrupt the effects of said spell by preventing it to be released.

So what is my point?

Based off of these relationships, we can come to the conclusion that there is a time period of the "Casting" of the spell (using gestures, chanting, drawing materials) that is responsible for drawing the energy.

And there is a second stage where the magic is "released" after it has been successfully channeled, separate from the material/gestural/singing phase, that can be interrupted and cause a waste of energy if it is not released.

Due to Counterspell causing the failed spell to waste a spell slot, we can understand that it prevents the latter of the two effects (stopping the spell from being released, but not drawn), which means that by the time Counterspell has been cast, the required rituals of the failed spell are already completed, allowing the targeted caster to use their hands/voice/materials for a new spell (such as a counter-counterspell).

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    \$\begingroup\$ What about spells with longer casting times? In this case, you are "casting" the spell for minutes if not hours. If I cast a spell during that time I could be casting multiple spells simultaneously, no? \$\endgroup\$ – David Coffron Jul 10 '18 at 22:49
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    \$\begingroup\$ @DavidCoffron Spells with longer casting times require concentration to cast, and require you to use your action every turn to continue casting the spell: dndbeyond.com/compendium/rules/basic-rules/… \$\endgroup\$ – V2Blast Jul 10 '18 at 23:46
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    \$\begingroup\$ @V2Blast If I cast a bonus action spell then? Mending is a cantrip with a 1 minute casting time. \$\endgroup\$ – David Coffron Jul 10 '18 at 23:52
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    \$\begingroup\$ @V2Blast reaction spells can still be cast. \$\endgroup\$ – Rubiksmoose Jul 11 '18 at 0:10
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    \$\begingroup\$ @V2Blast that's why I said mending. You can still cast cantrips of you cast a bonus action spell. \$\endgroup\$ – David Coffron Jul 11 '18 at 11:48

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