Can you ready an action that you don't have yet?

[ATHATH]

Is the following possible?

1. Alice readies an action to breathe fire over a certain area after Dragon's Breath is cast on them.
2. Bob casts Dragon's Breath on Alice.
3. Alice's readied action triggers, expending her reaction to breathe fire over that area.

[LumenPlacidum]

I would allow it. It's a huge investment of resources - if something happens to prevent it then Alice just completely lost a turn.

Please note that this wouldn't work with a spell that you don't have until someone passes you something (component, wand, whatever), since you actually cast the spell with the ready action and concentrate on it until your reaction happens.

[Composer99]

When thinking about these sorts of questions, it's useful to remember that D&D 5e combat is a turn-based abstraction overlying a very much not turn-based undertaking.

In the fiction of the game, Alice and Bob don't take turns whose order is determined by an initiative roll. If Bob can cast dragon's breath and likes to cast it on Alice, it makes sense that they would come up with a tactical plan whereby Alice waits to act until Bob casts dragon's breath.

So, yes, I would say you can ready an action that you don't have yet. (Maybe not in every case that comes up where such a thing might happen, but certainly in the case presented in the OP.)

[strangebloke]

stuff like this is why I like side initiative. The players are free to pick their order on their side's turn so coordination becomes a lot easier.

[Man_Over_Game]

I'm always a big fan of Risk/Reward balance. If it costs a lot, and it's sensible, it should do a lot.

Ready Actions don't do that, for almost anything. They make you predictable, make you take great risks, can be interrupted (where Actions generally cannot), and usually interacts directly with the ongoing circumstance (while Actions are generally generic).

So anything that buffs Ready Actions gets my vote, doesn't matter what it is. If you happened to make Ready Actions better than normal Actions somehow, I'd say "It's a good start".

[heavyfuel]

Alternatively, you could allow Alice to delay her turn, which I was surprised can't be done by RAW in 5e. If you win the initiative, there's no way for you to delay your turn, which should definitely be possible.

[Lunali]

stuff like this is why I like side initiative. The players are free to pick their order on their side's turn so coordination becomes a lot easier.

Alternatively, if you still want individual initiative to matter, put the initiative slots in order and let the players decide who goes in each slot.

[Frogreaver]

stuff like this is why I like side initiative. The players are free to pick their order on their side's turn so coordination becomes a lot easier.

I also find that method speeds up play as well.

[huttj509]

Alternatively, you could allow Alice to delay her turn, which I was surprised can't be done by RAW in 5e. If you win the initiative, there's no way for you to delay your turn, which should definitely be possible.

It's not possible in part because of the changes they made to abilities that would be "until the next round" type abilities in prior editions. "Lasts until the end of your next turn." Delay adds the possibility of jockeying initiative order to get more use out of those abilities.