[RPG] In case a trigger for a readied action is someone else’s reaction, what is resolved first

dnd-5ereactionsreadied-action

I asked if you can ready an action with someone's reaction as a trigger. The answer is YES.

But I'm still not sure – in such a case (i.e. a trigger for reaction being another reaction) – which reaction is resolved first, the triggered one or the triggering one?

Does the readied action interrupt someone else's reaction that triggered it? Is there a possibility of a chain of such consecutively triggering and consecutively interrupted reactions?

Best Answer

The trigger is resolved first

From the rule on the Ready action:

… take your Reaction right after the trigger finishes …

This applies specifically to the Ready action; Reactions that don’t depend on the Ready action (e.g. opportunity attacks, reaction spells) have their own rules.

Some of these, like Counterspell , specifically interrupt the trigger (so, yes, you can Counterspell a Counterspell). Others don’t. And one, Shield, has a weird time-travel effect.

However, for anything hanging off the Ready action, the trigger gets fully resolved first.

You can't take both Dash and Ready actions

Normally you don't "prepare a reaction". You take the Ready action instead. See Player's Handbook, page 193, "Actions in Combat"

Sometimes you want to get the jump on a foe or wait for a particular circumstance before you act. To do so, you can take the Ready action on your turn so that you can act later in the round using your reaction.

Then you use you reaction (if still available) to actually perform the readied action when trigger occurs. You spend both your Action and your Reaction in this case. Therefore, you can't use your action to Dash after you declared a readied action, because it is already spent.

Unless you have an extra Action, or you're a Rogue

As notices by @NeilSlater, a Rogue has his Cunning Action feature, which allows him to use a bonus action for Dash. You can take the Ready action afterwards. However, this doesn't give you more movement than usual, since you just can Dash twice.

Also, you can't use "my turn ends" trigger

PH requires "perceivable circumstance" for a trigger:

First, you decide what perceivable circumstance will trigger your reaction.

Turns are game mechanics, they don't exist in the game world, hence, are not perceivable by the character, see Can you ready an action for "immediately before my next turn"?

You can move up to your speed using the Ready action

However, the question remains — what if you spent all your movement, and then take the Ready action to move 30ft more? Yes you can do this, providing your speed is 30 (or more) feet:

you choose the action you will take in response to that trigger, or you choose to move up to your speed in response to it

Ready action works like a "delayed Dash" in this case.

[RPG] Do you lose concentration on a Readied spell when you use your reaction for something else

You don't lose concentration, but you can't cast the spell.

This really isn't any different than Readying the spell and either not getting the trigger you expected or opting not to use the trigger when it arrives.

But it is kind of a tricky situation, and while losing concentration makes sense at face value, there are rules to support that it doesn't - even if they don't really matter in the end.

Ready action

Let's begin with the rules around Readying (PHB, chapter 9) a spell (emphasis mine):

When you ready a spell, you cast it as normal but hold its energy, which you release with your reaction when the trigger occurs. To be readied, a spell must have a casting time of 1 action, and holding onto the spell's magic requires concentration. If your concentration is broken, the spell dissipates without taking effect.

So we know that when you are readying a spell, you are concentrating on it. And you are waiting on the trigger so you can expend your reaction and release the spell.

Concentration

The four normal means of losing concentration(PHB, Chapter 11) are:

Casting another spell that requires concentration
Taking Damage (and then failing a save)
Being incapacitated or killed
Actively choosing to end concentration

You have not crossed through any of these gates, so concentration is still up. There is nothing in the Ready action that says choosing not to release on a trigger (or the trigger failing to occur) equates to dropping concentration.

So what about the spell?!

Well, you are actively concentrating, but if you've expended your reaction, then you have no means of releasing the energy. Without the ability to trigger the release, the concentration remains until you lose your Ready at the start of your next turn (barring one of the effects that specifically removes concentration)

At that point, the spell energy dissipates without the triggering action and you can begin your turn as normal (minus any spell slot that may have been used for the Ready.)

Penalties

Given that the PC has already expended an action (and possibly a spell slot) and chosen not to use it by taking up their reaction, I really don't see a reason to further penalize them with the loss of their class feature as well - especially when it isn't fully supported in the written rules and only in a Sage Advice ruling.

But even with that SA Ruling, I don't see it as very well supported as I show above with this alternate ruling. They have taken their action to hold the spell, but have not released it. I see this as identical to ignoring the trigger and holding it until their next turn. The difference is simply that they used their reaction for something else, not that they dropped their concentration.