Confession time! A recent comment on my Shield Master feat post revealed that I have been playing the Ready action wrong on my table. Ooops! 🙈
Anyhow, I figured there are a probably a few other folks doing the same, and it might be worth revising the exact text of the Player’s Handbook, as well as some of Jeremy Crawford’s tweets, which are always useful for official rules clarifications, in a bid to get it 100% right from now on.
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, which lets you act using your reaction before the start of your next turn.
First, you decide what perceivable circumstance will trigger your reaction. Then, 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. Examples include “If the cultist steps on the trapdoor, I’ll pull the lever that opens it,” and “If the goblin steps next to me, I move away.”
When the trigger occurs, you can either take your reaction right after the trigger finishes or ignore the trigger. Remember that you can take only one reaction per round.
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. For example, if you are concentrating on the web spell and ready magic missile, your web spell ends, and if you take damage before you release magic missile with your reaction, your concentration might be broken.
The Ready action hasn’t seen much use on our table, but when it has, I believe we haven’t adhered to the strict interpretation of the rules, but we have rather used the Ready action to defer our turn until later in the initiative chain, using our reaction as the cost.
HOWEVER, holding your action OR your move, and holding your entire turn are pretty different things. For example, your turn might include not only an action, but a bonus action and movement as well. While your action encompasses literally just your action, and in fact doesn’t even feature the additional attacks from the Extra Attack class feature, which states:
Beginning at 5th level, you can attack twice, instead of once, whenever you take the Attack action on your turn.
The Ready action lets you ready any action you can take, including Attack, but Extra Attack is on your turn. https://t.co/5txJB0u8MH
— Jeremy Crawford (@JeremyECrawford) May 30, 2015
The ruling probably sense: if not for that, you could probably get up to all kinds of tricks and easily lure enemies onto the full force of your offensive arsenal at highly opportune moments; but it certainly makes using the Ready action a much more niche choice than I previously believed it to be.
Even holding a spell is a little dangerous as, if for some reason the trigger doesn’t occur, you lose your spell slot, plus – if you take damage before releasing the spell – you could lose concentration before you’ve even cast.
A readied spell's slot is lost if you don't release the spell with your reaction before the start of your next turn. https://t.co/0K59zeZLjX
— Jeremy Crawford (@JeremyECrawford) August 29, 2015
(Note for DMs: as the spell is actually cast on the Readying creature’s turn, and then held, any successful use of counterspell would need to be at the point of casting, not at the point of release).
How to Use Ready to Good Effect
One thing worth pointing out is that there’s nothing to stop you moving on your turn and taking a bonus action (that isn’t predicated on you taking your Action), and then taking the Ready action. So you don’t necessarily have to sacrifice your bonus action and movement in that round, it’s just you have to take them on your actual turn.
Otherwise, I’d suggest using Ready when you are in a great strategic position you don’t want to give up, and/or for waiting for enemies to get within range of a spell, or short range of a ranged weapon (instead of shooting at disadvantage at long range). These tactics make more sense the less attacks you have! As once you get Extra attacks you will have to sacrifice them when you take the Ready action.
You might, as well, be forced to take the Ready action in order to deal with a ranged foe who keeps disappearing behind total cover after they shoot at you. The trigger in this case would be them reappearing, at which point you could fire off a spell or attack, hopefully disabling the threat before they can attack again. (This is a good tactic for DMs to remember, for dealing with PCs that attempt to use total cover in between attacks!).
I’ll finish with a question: have you been using Ready correctly on your table, and, if so, how have you used it to good effect? I’d be particularly interested to know if it can be used regularly to good effect, as opposed to just for gaining a very specific situational advantage.