Can the trigger criteria for a readied action be as simple as casting after an ally's attack?

If so, are there measures to prevent a pseudo double spell casting like the following example?

Player B: "I would like to ready my action - to cast the Slow spell centered on 'this' enemy, right after Player A makes his attack." (Player A goes right before Player B in initiative.)

Right after Player A makes his attack the Slow Spell is cast.

Player A then ends his turn.

Player B now has a full turn.

Is this a plausible scenario, or does it break the game's mechanics in any way, shape, or form?

Granted, you delay the 1st turn's spell being cast, but you almost guarantee that your spells occur back-to-back without a chance for an end-of-turn save to remove the spell's effects.

Possible issue examples:

  • Slow -> disintegrate/fireball.

  • Hold Person -> Hex + Scorching Ray at higher levels

  • 2
    \$\begingroup\$ Great question! I like your examples of possible useful applications of this idea. A small issue with the last one: Hold Person and Hex are both Concentration spells, so you couldn't have them both active at the same time. I get what you're going for, though. It is a very neat idea to hold a Hold Person spell until after that creature's turn. \$\endgroup\$ Apr 28, 2019 at 23:42
  • \$\begingroup\$ Player B does not have a full turn, it just has an action \$\endgroup\$
    – András
    Apr 29, 2019 at 7:39
  • \$\begingroup\$ Do note that Readying a spell requires concentration, which would automatically end any other concentration spell. So Hold Person -> Readied Hex would be no different than casting Hex on your turn. \$\endgroup\$ Apr 29, 2019 at 13:21

2 Answers 2


This is valid by the rules, but might get called out as metagaming

As Token's answer adequately covers, what you've described is valid according to the rules for readying a spell. However, depending on the style of play used at your table, your DM may disallow it because it is metagaming; that is, having your character act based on out-of-character knowledge. Here's what the rules have to say about rounds and turns in combat (emphasis added):

A typical combat encounter is a clash between two sides, a flurry of weapon swings, feints, parries, footwork, and spellcasting. The game organizes the chaos of combat into a cycle of rounds and turns. A round represents about 6 seconds in the game world. During a round, each participant in a battle takes a turn. The order of turns is determined at the beginning of a combat encounter, when everyone rolls initiative. Once everyone has taken a turn, the fight continues to the next round if neither side has defeated the other.

Note the sentence I have highlighted in bold: within the fiction, characters in the battle aren't really taking turns. They're all fighting simultaneously and continuously, but because simulating real-time combat is not practical, we compromise realism in favor of simplicity and have them all take turns in initiative order. However, this means that the initiative order is part of the game, not part of the game world, and thus the initiative order of combat is out-of-character knowledge, which means using that knowledge to guide your character's actions constitutes metagaming.

So, if you attempt to use this "double-spell combo" at a table that values in-character role playing and frowns on metagaming, you will probably be called out for choosing a trigger condition that has nothing to do with your readied action. You are effectively trying to find a loophole that lets you specify "after the target's turn ends" as your trigger in order to deny the target an end-of-turn save. On the other hand, other tables are happy to embrace the turn-based gameplay and treat combat like a game instead of a simulation, and they will instead congratulate you on the neat trick you found. You probably already have a pretty good idea of which kind of table you're playing at, but if not, you should ask your DM ahead of time before you try to pull out this trick during a session.

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    \$\begingroup\$ I wouldn't rush to call this metagaming, since in combat (even in a fantasy world) actions you decide to take can be and often are influenced by what those around you are doing at any given moment. Thinking tactically about the situation and making decisions based on observations in the midst of a fight is exactly what someone with high intelligence (like a Wizard) would do. You can see your Fighter friend laying into some hapless Orc and decide you want to get in on that in the most advantageous way possible without it being metagaming. \$\endgroup\$
    – Seidr
    Apr 28, 2019 at 23:38
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    \$\begingroup\$ @Seidr I would say that it is definitely metagaming if your motivation for choosing a trigger condition is to approximate an invalid trigger ("after the enemy's turn ends"). However, there is definitely a gray area. If the choice of trigger is strategically defensible but your real reason for choosing it to release the spell after the enemy's turn, is it metagaming? I think these things vary from table to table, which is why I said it might be disallowed as metagaming. \$\endgroup\$ Apr 28, 2019 at 23:46
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    \$\begingroup\$ I agree with Ryan. It is especially questionable in this case as the trigger (an ally's attack) is something you'd usually want the spell (Slow or Hold Person) to be active for. Thus, choosing to activate the spell after such an occurrence is hard to justify for any reason other than the order of respective creatures' turns. It might be more defensible if your ally had several attacks in one turn, and you were thus ensuring that the rest of those attacks benefitted from this spell. \$\endgroup\$ Apr 29, 2019 at 0:11
  • 3
    \$\begingroup\$ @Seidr The OP stated that the motivation was to deny an end-of-turn save by delaying the spell's release until after the target's next turn. Otherwise there is no reason not to cast the first spell immediately in either of the OP's examples. \$\endgroup\$ Apr 29, 2019 at 0:50
  • 2
    \$\begingroup\$ @RyanThompson, denying a save is a very valid, very in-game reason to delay your casting. Yes, rounds are a meta-concept, but you could rephrase it: "the longer I wait between my spells the more likely it is the target shakes off the effect, so I delay the first as much as I can" \$\endgroup\$
    – András
    Apr 29, 2019 at 7:49

Yes, that can be a declared trigger for the ready Action.

The rules for readying that apply here:

Ready, PHB p. 193

First, you decide what perceivable circumstances will trigger your reaction... When the trigger occurs, you can either take your reaction right after the trigger finishes or ignore the trigger.

This does allow for the pseudo double spellcasting that you mentioned, though this may not be as much of an issue as one might think.

To accomplish this the PC has to take on a few risks and drawbacks:

  • He needs to maintain concentration on the spell throughout the entire round; if he loses concentration, he loses the spell.

  • It's also possible that the ally (by his own volition or otherwise) might not attack in order to complete the trigger. This would give the PC in question no opportunity to cast his spell.

  • Should the PC want to use his reaction for something else, he will have to choose between that and his readied spell. A hefty cost when considering counterspell and other useful reaction spells.

  • The PC will also not be able to concentrate on any other spell while he holds his readied spell. Also a hefty cost.

  • If the spell cast by the PC had any perceivable casting components, he has then telegraphed his next move. Hostile creatures that understand a spell is being cast may act accordingly. (The PC can't counter the counter!)

This does not break the action economy or constitute an exploit. I can't extrapolate the player's reasoning for doing this, but it does seem to be a rather suboptimal choice to incur all of those negatives instead of an exploit that breaks anything. There is the payoff of being able to disadvantage the creature on its saving throw against his next spell, but, at least to me, it doesn't seem to outweigh all of the opportunity cost involved.

  • \$\begingroup\$ The issue isn't necessarily concentration - it's combo'ing spells as a solo PC. Slow specifically makes it that units affected are disadvantaged on DEX save throws which means you're free to shoot a Fireball/Disintegrate on your turn. \$\endgroup\$
    – Wheelium
    Apr 28, 2019 at 21:56
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    \$\begingroup\$ The mention of concentration was to show that this tactic has some risks attached to it, making it a bit more 'fair' and not so much a perceived exploit. I maintain that the rules seem to allow this. \$\endgroup\$
    – Token
    Apr 28, 2019 at 21:56
  • 4
    \$\begingroup\$ I would also add that if the ally does not attack for whatever reason the spell slot is wasted, which is yet another risk. Not to mention the caster would be "wasting" their earlier turn in order to ready the spell. The turn is essentially just being pushed back in the order, it's not more "broken" than casting on your own turn, you only take on additional risk. \$\endgroup\$
    – Seidr
    Apr 28, 2019 at 22:00

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