D&D 5E Legal Ready action triggers and order of resolution

[morikahn]

I've tried to get some clarification on this issue with the Ready action on reddit and twitter with no such luck. Responses haven't been what I was looking for.

I understand that Ready actions can only be used in combat, so for the sake of this discussion, we'll just assume all examples are in the middle of a combat situation; many turns have already passed by so initiative and surprise are not an issue.

The rules state the Ready action occurs after its trigger has finished, but can triggers for the Ready action specify the beginning of an action? Then when the beginning of an action finished and not the entire action itself... does the Ready action fire?

Examples:

• If opponent starts to cast a spell I'll do ...
• If dragon starts to use its breath attack I'll do ...
• If opponent tries to run away i'll do ...

If you answer 'yes' to the above, then this is possible:

• When a rogue tries to run for cover, an archer Readied to 'shoot him if he tries to move' gets his shot off first before the rogue gets to cover.
• When a mage attempt to cast an Invisibility spell, a player Readied to 'cast Magic Missile on him if he attempts a spell' gets to attack him before the Invisibility takes effect (Magic Missile spell requires a visible target).
• When a caster attempts to cast Magic Missile on a player that has used the Ready action to 'run through the door and out of line-of-sight if the mage starts casting a spell" the player does just that, preventing the mage from targeting him.
• When a dragon starts to use its breath attack, a tightly packed group of goblins that have used Readied actions to "run if the dragon tries to breath fire on us" all run in different direction, making it impossible for the dragon place them all in with the AOE of its breath attack.

Now, if you answered 'no', then that means:

• When an archer uses a Readied action to 'shoot a rogue if he tries to move', the Rogue can move behind nearby full cover and avoid being shot, thus wasting the archers use of the Readied action.
• When a player readies a 'Magic Missile spell to attack an enemy spell caster if he attempts to use a spell', the enemy spell caster can use the Invisibility spell to avoid being targeted, thus wasting the players Magic Missile spell.
• When a player uses a Ready action to 'run out of sight if an enemy spell caster attempts a spell', he will not get to move until after the spell caster has finished that spell.
• A dragon that readies a Breath Attack on a group of goblins 'if they try to run' won't be able to target them all if they run in all different directions.

A lot of the issues that arise come from using the Ready action to avoid an attack, such as trying to move yourself out of range, out of line-of-sight, or out of the area of effect of a spell or spell-like ability

Attacks of Opportunity are reactions, same as the Ready action, and they trigger right when a character attempts to move out of melee range of an opponent, so there is precedent that reactions can fire in the middle of an opponents action.

I'm looking for what would be the most legal ruling, such as what I could expect to see at a convention game.

 

[Sorcerers Apprentice]

I don't think the kind of ruling you are looking for exists. Defining what a trigger for a readied action can be is left pretty much entirely up to DMs discretion.

 

[TheCosmicKid]

A lot of the issues that arise come from using the Ready action to avoid an attack, such as trying to move yourself out of range, out of line-of-sight, or out of the area of effect of a spell or spell-like ability

Attacks of Opportunity are reaction, same as the Ready action, and they trigger right when a character attempts to move out of melee range of an opponent, so there is precedent that reactions can fire in the middle of an opponents action.

I'm looking for what would be the most legal ruling, such as what I could expect to see at a convention game.

Like @Sorcerers Apprentice said, I don't think you're going to get a hard-and-fast ruling, and are going to have to use your discretion. This is pretty much how 5E is intended to work. Even at convention games, the rulings are going to vary somewhat from table to table. (If you watch WotC's liveplays at all, you may have noticed that Chris Perkins flagrantly disregards rules whenever it would be more interesting to do so or when they just slip his mind.)

But as far as my discretion is concerned, none of the effects you've described under the "yes" alternative strike me as unreasonable. The characters are spending their actions on their turn to pull these things off; they're not exactly free or easy to do. You've already noted that opportunity attacks require the premise that reactions can interrupt other characters' actions, and I can offer you another big example in disrupting spells. Counterspell, like an opportunity attack, explicitly requires an interrupt. And for characters without access to that spell, readying an attack to hit the enemy wizard if he tries to cast is a standard tactic going back multiple editions.

So I'd definitely allow it at my table.

 

[morikahn]

But as far as my discretion is concerned, none of the effects you've described under the "yes" alternative strike me as unreasonable..

Yeah, Cosmic, I'm actually favoring that it is possible to interrupt an action with Ready, as it does seem very reasonable, while the reverse seems unreasonable. It also involves a lot of risk as the character using the Readied action is taking a gamble.

Its opens up a lot of tactics that could potentially cause opponents to waste limited attacks, and I know this could really tick people off in a game.

 

[UngeheuerLich]

I will decide on a case by case basis. Tries to cast a spell? How do you know? Arcana check? Depending on success you may be fast enough to act before the mage finishes it. Better trigger may be. When he starts wiggling his hands. I would allow the mage to use deception to hide his movements maybe.

Many rules are serving you better if you try to imagine how the situation looks like in your mind and don't think in game terms.
In the rogue case you can decide how far away the cover is and if it is very close it might be as simple as a dexterity contest. Or again deception to create a distraction and then the rogue gets away automatically or has advantage on the dex check.
That is the strength of RPGs. You create a story. Your characters don't just start casting a spell when a knife is on their throat. The rogue does not simply walk behind cover. It is rather like that:

The guard points with his crossbow right at your face and shouts: hold still and don't even try to do your foul magics. Drop the staff.
The mage smiles and says: ok, ok. I will lay it down on the ground.
The mage sllwly goes on the ground. Lays the staff down and subtely grabs some fine sand from the ground. (sleight of hand check).
Then the mage lets his dancing light flare up a bit and throws the sand, vocalizing his formula and the guard strats falling asleep loosing his crossbow bolt a little bit too late. (Dex contest one by the mage with a difference of only 1. So the guard gets a shot with disadvantage that misses the mage)

The rogue at gunpoint makes a step to the left and jumps to the right.
Deception check followed by acrobatics. Against insight and then against dexterity with advatage or disadvantage or neither depending on the previous result.

 

[Enevhar Aldarion]

Just remember that rules for delaying your action are not part of 5th Edition, so if any of your examples require you to hold or delay, then they are not valid as a Readied action.

 

[morikahn]

I will decide on a case by case basis.

Well, each example could have extraneous conditions. As you pointed out, a DM might require a skill check for the character using Ready action to recognize his or her trigger fired.

But the central focus of the question is can one character interrupt another character mid-action through a Readied reaction which might diminish the effectiveness of the original action.. or perhaps negate its effect entirely.

If I was Dming at a convention would I get tarred and feathered if a player cast Lightning Bolt at an enemy mage, only to find the mage had Readied Wall of Force to be cast near the player, thus reflecting the Lightning Bolt back at himself and his nearby party members?

It allows for some very tricky situations.

 

[Plaguescarred]

I think it's usually easy to figure what the Readier wants to accomplish and if he wants to interrupt a triggering event, then Ready An Action should work as intended. So when a an archer Ready An Action to attack a rogue that will run for cover, he should attack the rogue before he finish doing so for exemple.

 

[UngeheuerLich]

Well, each example could have extraneous conditions. As you pointed out, a DM might require a skill check for the character using Ready action to recognize his or her trigger fired.

But the central focus of the question is can one character interrupt another character mid-action through a Readied reaction which might diminish the effectiveness of the original action.. or perhaps negate its effect entirely.

If I was Dming at a convention would I get tarred and feathered if a player cast Lightning Bolt at an enemy mage, only to find the mage had Readied Wall of Force to be cast near the player, thus reflecting the Lightning Bolt back at himself and his nearby party members?

It allows for some very tricky situations.

Make it a dexterity check. Advantage at close range. disadvantage at long range. Make it a perception check. I mean if you have to fiddle in your component pouch while the readie wall of force already was basically cast and is held with concentration... I think the PCs who argue for one side would also argue for the other side if positions were swapped.

 

[Greenstone.Walker]

Trying to adjudicate the start of an action gets really complicated and metaphysical, real fast.

When does casting a spell begin? When the mage starts gesturing? When they start talking? When they draw breath to talk? When they first think about casting a spell?

How does the witness know the drawn breath is a precurser to a spell? How does the witness know the spell is invisibility or not fireball or misty step or something else?

When does a move start? When the muscles tense? How does the witness know that the tensed muscles are the start of fleeing or the start of charging or the start of something else?

Simplest answer (because D&D is a simple game, not a reality simulator) - they don't.

Reactions are not interrupts - they happen after the triggered action. "When the target moves" triggers after they have moved some distance (usually one square), thus the archer can shoot the rogue before she reaches cover. "When the target casts a spell" triggers once the target has finished casting, thus the magic missile won't go off.

There are exceptions, and they are all listed in their description. For example, counterspell, shield, sentinel feat.