If I ready an action (spell) in response to a companion's attack, what is a fair GM ruling over the order of events?

Question

In our campaign, I have a cleric who wished to use Ready an Action as his move. His idea behind this was that he wanted to ready Guiding Bolt and the condition he set was that, when one of the players (fighter) attacked a creature (one of two trolls) he would release the bolt beforehand. Therefore the fighter would have advantage on her attack if the Guiding Bolt hit first.

I ruled that the fighter hit first, but I'm not so sure now - and I feel like I was unfair in my ruling, maybe. I can see both points of view:

1. If I was the cleric readying my spell, I would cast the spell as soon as I noticed my fighter companion's intention to attack a creature.

2. But, also if I'm the fighter and I'm 5' away from a creature, maybe my attack would land first, before the Guiding Bolt.

I would like some RAW guidance on this please. But, if not explicitly available, then a response with lived experience of a GM on a similar ruling to do with resolving the order of events.

Answer 1

@Medix2 proposes a well-cited answer for the RAW scenario, but I will propose some solutions to turn this ruling in your party's favor.

The cleric is putting a lot on that readied action: concentrating until their trigger occurs, and the potential loss of a spell slot if the trigger doesn't occur. I think there are opportunities here to translate your cleric player's intent into the game such that it both works the way they want, and plays nicely enough with the RAW.

Character Communication

From 'Other Activity on Your Turn' in the basic rules:

[...] You can communicate however you are able, through brief utterances and gestures, as you take Your Turn. [...]

One way you could make this work, and potentially invite some combat roleplay, is to rule that the characters need to verbally coordinate such attacks, or create some other system of communicating this intent. The cleric holds their spell for the fighter's signal and yells to the fighter 'Let me know when!'; then the fighter, on their turn, yells to the cleric "Now!" while making a mad dash toward their target, sword in tow. This seems a clear enough 'perceivable circumstance' to act as a trigger, and eliminates the vague wording of "when the fighter starts to attack".

If you have particularly roleplay-averse players, or if you want to introduce this method to them naturally, this character interaction could be described by you, the DM, to explain how the intended actions of the players can actually play out in the world in a way that is friendly with the rules. I feel that this is likely the best solution, as it both explains why the previous trigger didn't work and sets a model to translate player intent to character action moving forward.

Simultaneous Effects

This ruling is less strictly rules-friendly, but is the way I rule readied action triggers in my own games. The term 'perceivable circumstance' is not a defined game term, and is subject to your interpretation. Because of this, I would allow an ambiguous trigger such as 'when X starts to attack', but consider the triggered spell/attack/movement a simultaneous effect with the attack. Xanathar's Guide proposes an excellent way to handle Simultaneous Effects in Chapter 2:

[...] If two things happen at the same time on a character or monster's turn, the person at the game table - whether player or DM - who controls that creature decides the order in which those things happen. [...]

If you handle it this way, then the fighter can choose to allow the bolt to go off before their attack. And, as a bonus, if the cleric attempts to ready their action for when an enemy is about to attack, that enemy will probably decide that their attack resolves first, as the original readied action rules would have dictated. In RP terms, a cleric and a fighter who have been travelling and fighting together for some time would likely understand each others' intents in combat better than they'd understand that random enemy they stumbled upon; in short: coordinating with teammates is easy, but enemies are unpredictable. This ruling changes very little about how readied actions work, yet allows a lot of Rules as Fun combat interactions that might not otherwise work.

Answer 2

The trigger for a Readied action can be any perceptible event

[...] First, you decide what perceivable circumstance will trigger your reaction. Then, you choose the action you will take in response to that trigger [...]

Because of this, a trigger of "When an enemy comes within 5 feet of a team member" (or the opposite) is a perfectly valid trigger. As is "When a creature moves" which would cover this case and many others simultaneously.

We also know that reactions happen after their trigger but that doesn't change anything here because the attack happens after the movement anyway. There is "time" between the movement and the attack for the Readied action to occur.

[...] When the trigger occurs, you can either take your reaction right after the trigger finishes or ignore the trigger. [...]

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The specific trigger of the start of an attack might work

This scenario is far less clear and I've written about it before. 5e does not have a "start to attack" phase or anything of the sort so what exactly happens with this trigger is not entirely clear. I would wager that most attacks are going to be perceptible but I likely wouldn't allow a Readied action to occur after the attack has started but before it has finished. This is simply a personal choice of mine and we have numerous related questions on Readied actions occurring in the middle of some other single event:

• Can a creature react to being targeted by a missile attack from a non-Hidden foe?
• If I ready an action to an enemy's attack targeting my ally, and my reaction helps my ally move, does the enemy get to retarget?
• When the artificer's Mechanical Servant uses its reaction to make a melee attack, does it interrupt the triggering attack against the artificer?
• Can a thrown javelin be catapult-ed back?
• Can you cast the Darkness spell on an in-flight arrow using the Ready action?
• Can you use a readied action to teleport out of the way of a weapon attack?
• Is it possible to interrupt spellcasting?

Answer 3

You should be letting the ability resolve in the order that the players want them to resolve.

Even if this wasn't possible under the Rules as Writen, it definitely falls under to Rules as Fun/Rule of Cool. If two players are trying to work together to take down a challenge, that should 100% be encouraged,and you should certainly feel free to bend the rules slightly.

It's entirely reasonable to allow this to happen, as long as the players are able to communicate effectively to each other in the combat, i.e, speak the same language, and can see/hear each other. Yelling "wait until my spell lands to strike" takes little enough time to say that it can reasonably fit into one turn, and the fighter can certainly delay their attack until the spell lands on the troll.

Answer 4

As per the rule on Ready Action, The action is ALWAYS released AFTER what triggers ite. So the player cannot use that ready action that way the rules do not allow it. He needs to come up with a better one.