If a readied actions is triggered by the readying of another action, can the action being readied also resolve?

Question

In our last session the party was ambushed by 4 drows... (Arcane Guard - City of the spider Queen). The guards were willing to talk but 3 of the drows had electricity crackling over their hands, so the players knew the drows had readied a Lightning Bolt. They where going to cast it as soon a player made an aggressive move. One player (sorcerer) started readying a fireball that he would cast as soon as the drows made an agressive move, so the arcane guards casted the Lightning Bolts as a reaction when they saw the fiery glow appear over his hands. So far no problem...

But then the players and me had a discussion, they thought the sorcerer could cast his fireball now, I didn't agree because he just started readying it, and in my opinion normal combat should begin and the sorcerer just needs to wait his turn...

We decided that the sorcerer could cast his fireball (to be honest, the party was going to have a hard time otherwise...)

But I'm wandering, what is the correct way to resolve this situation? Could the sorcerer cast his (not yet readied) fireball as a response to the readied action of the drows?

As noted in the comments, the effects (crackling electricity and fiery glow) aren't normally seen when readying a spell. This is also not a houserule of ours... It was story telling wise to give the platers a warning that hey were in danger... I judged, since the players could see the drows had readied a spell, the drows could also notice the player readying a spell.

Answer 1

To ready an action, you should have rolled initiative already.

Being "ready" to cast a spell if something happens while you're not in combat just makes it so you're not surprised when the other party stops parlaying and starts casting an offensive spell, but even casting that fireball should be preceeded by an inintiative check. Did the guards go first? Well, they noticed the sorecere doing something suspicious but reacted faster. They don't really need to prepare anymore, they can just cast whatever they want (and they're not forced to pre-choose a spell, and the sorcerer might change idea and cast something different, but it's too late to stop combat. Yet, he might surrender).
If the guard lose initiative, well, the fireball goes first.

So, what happened in the scene is that nobody did nothing. They mentally prepared to the idea of casting something if things got awry but nobody did anything aggressive. Combat starts as usual.

Answer 2

Zachiel's answer is correct, but here's a walkthrough just in case.

Consider not streamlining encounters...

It sounds like the group knows the rules but dispenses with some to speed up play. This is totally understandable. But it also sounds like the players might need more granularity to realize their play style.

In our last session the party was ambushed by four drow...

The drow made Stealth skill checks when the party was near enough to make Perception skill checks and the drow all won. It's the surprise round. Everyone makes initiative checks. The PCs are unaware combatants, so they won't be acting during the surprise round.

The PCs, at this point, are unaware combat has begun.

One drow is willing to talk but three of the drow ready lightning bolt spells...

At this point any drow can choose to reveal their positions to parley or, if in an appropriate position, parley from their hiding places (likely also revealing their positions, or at least giving the PCs another opportunity to make Perception skill checks). Breaking stealth to reveal themselves to the party probably takes the drow's actions during the surprise round. Taking a free action to speak is possible for both sides, so a parley during the surprise round is totally possible assuming negotiations are short ("Speaking more than a few sentences is generally beyond the limit of a free action").

Any of the drow who don't take other actions can take a standard action during the surprise round to take the ready action, setting the action as cast the spell lightning bolt and the trigger as When a PC takes an aggressive action.

• The spell lightning bolt may be an unwise choice unless tactical circumstances permit the drow to avoid catching any of their fellows in the spell's rather large area of effect (A targeted spell might've been a superior tactical choice.) But they're drow; maybe they want to catch their fellows accidentally in the bolt's area.
• This is a really broad trigger for the ready action, and the GM may mandate that the drow need to be more specific as to the nature of the trigger, maybe requiring instead the trigger be a specific action, like If a PC casts a spell or If a PC draws a weapon.

The sorcerer started readying a fireball. The drow view this as aggressive so they cast multiple lightning bolts...

The GM's made it clear to the players beforehand that the process of readying an action is obvious and that the outcome of that ready action is equally obvious. That's not the case by default, but, since there is no case by default, these house rules are as good as any. Note that a successful Perception check versus the drow who had also taken the ready action would've revealed that they had taken the ready action to cast lightning bolt.

• This GM is not entirely comfortable with a house rule like Foes who can perceive the creature know when a creature has taken the ready action and know what action the creature will take with that readied action. Preparing spell components to cast a spell is a free action, so it's not necessary for a creature to reveal to his foes that he's taken the ready action to cast a spell; the components can be prepared after the trigger action's come about.
• The obviousness of the creature having readied an action can also be disputed. A creature that's readied an action doesn't take a penalty to its AC, for example, nor to any checks, and hasn't taken any other actions, either. That the opposition nonetheless (perhaps intuitively?) knows the creature's taken the ready action strikes this GM as weird.

...And, instead, taking encounters step by step

• Before Combat

  • The drow find hiding places. The PCs approach a position from which the drow may be perceived. PCs make Perception skill checks opposed by the drow's Hide skill checks.

• Surprise Round

  • Everyone makes initiative checks, but only aware combatants (the drow and any PCs who win the Perception versus Hide opposed checks) can take actions.
  • In initiative order, one drow emerges from his hiding place to parley with the PCs. The remaining drow ready to cast lightning bolt if a PC takes aggressive action.
  • Aware PCs also act (or, possibly, delay).
  • PCs that take aggressive action are subject to the drows' readied actions.

• Round 1

  • PCs and drow take their actions normally.
  • If the PCs take aggressive action before the drow's actions come up this turn, the drow's ready actions trigger and their initiative counts are reset. If the PCs don't take aggressive action before the drow's actions come up this turn, the drow can ready again (either the same way or differently) or take actions normally.

Answer 3

If a readied actions is triggered by the readying of another action, can the action being readied also resolve?

If you mean the chronologically first readied action, yes.

It doesn't matter if the party member's action is also a readied action, because their action to ready hasn't resolved yet.

A readied action

occurs just before the action that triggers it.

So the drow would cast their spell before the party caster completes readying the action to cast a spell.

This would also mean there's nothing to trigger the party member's readied action (yet).

But then the players and me had a discussion, they thought the sorcerer could cast his fireball now, I didn't agree because he just started readying it, and in my opinion normal combat should begin and the sorcerer just needs to wait his turn...

You were correct, "because he just started readying it" (he did not complete readying it), but not because of how "normal" combat begins, rather because of how readied actions work.

As others mention, it's probably easier if you use the strict "How Combat Works", although I don't call for initiative until the surprise round begins in the case where the party is entirely unaware, but the key point is you need to have initiative before anyone can act to delineate order. I would treat the parleying as inconsequential, out of turn free actions, though strictly, any more than what can be spoken in 6 seconds is not a free action.

And while Zachiel is absolutely correct, the party's initiative order is inconsequential when the entire party is surprised, at least during the surprise round. Even the drow's initiative order is inconsequential if all they do is ready actions. The problem with this approach is that it isn't clear to the players that the drow have already acted. Especially if they are hidden. Perhaps it shouldn't be clear. :)