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

[UngeheuerLich]

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.

I think it is really depending on the risk the attacker will take.
If the trigger is: When the rogue tries to run away, you have theb to make a decision when the rogue moves if he really wants to run away. If the trigger is the rogue moving at all then you just shoot... and maybe a bit too early when the rogue just wanted to surrender... i mean that is what happens a lot these days in US... one wrong move with the hand and a lethal shot is fired...

 

[Plaguescarred]

I think it is really depending on the risk the attacker will take.
If the trigger is: When the rogue tries to run away, you have theb to make a decision when the rogue moves if he really wants to run away. If the trigger is the rogue moving at all then you just shoot... and maybe a bit too early when the rogue just wanted to surrender... i mean that is what happens a lot these days in US... one wrong move with the hand and a lethal shot is fired...

When your trigger arise, you either take your readied action or you don't. If you Readied an Action to such trigger, when the rogue run you either shoot him or you don't. The risk of doing or not doing so is a case by case for sure.

 

[fjw70]

I would say that the readied action would happen after a specific trigger. You can't ready for someone starting to attack but you can for an archer drawing an arrow from the quiver (for example), or when the enemy moves one space. It would tied the trigger to a specific action in the game world.

 

[Shiroiken]

Totally DM discretion. In general, I have no issue with a Ready Action "interrupting" the trigger, but I would examine everything in a case by case basis. To consider your examples:

• When a rogue tries to run for cover, an archer Readied to 'shoot him if he tries to move'

I'd be okay with the archer making the attack. Remember, the entire round takes place in 6 seconds, so unless the rouge is directly adjacent to the cover, this will take time to do (giving the archer time to take the shot.

• When a mage attempt to cast an Invisibility spell, a player Readied to 'cast Magic Missile on him if he attempts a spell'.

Assuming this a spellcaster with Invisibility on their spell list, I'd be fine with it. The mage begins casting, as does the player, the target is already set once the missiles being to fly. The missiles fly true and strike the Mage (causing a Concentration check, because IIRC it's a Concentration spell). If the player doesn't have Invisibility, I'd require an Intelligence/Arcana check to know that a spell is being cast (rather than just random movements).

• 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"

My answer is a combination of my above answers. The target is set, and it will take time to get out of the way. Also, unless the character is a spellcaster with the spell on their spell list, I'd require an Intelligence/Arcana check.

• 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"

This gets tricky. I'd require each to give a location they're going to run to (because Ready requires specifics), so some would probably escape the flames.

Something to consider when adjudicating a Ready Action is the loss of the Action. IME if someone Readies, they usually can't actually perform the action until the trigger occurs. If someone could already perform the Action, but doesn't (as in every example you gave), there should probably be a reason (the archer has ordered the Rogue to surrender, for example). I can't understand why someone would Ready to run out of line of sight from the mage, when they could take an Action (such as an attack), then run out of the room. Same thing with the dragon.

The other thing to consider is how you describe a Readied Action as a DM. When I have a monster or NPC Ready, I tell the players something to describe the action. For the Archer, it would be the bow aimed at the Rogue. For the Mage (both examples), the player would be staring intently at the mage (possibly also looking at the door). In the case of the Dragon, the goblins would be tense and looking at their chosen run space. This can help players and NPCs make intelligent decisions, and might prevent the Readied Action from happening (depending on the intelligence and goals of the NPC, as well as the specific situation; in the Dragon example, it might not use it's breath weapon, buy rip them apart in melee).

 

[morikahn]

Its starting to sound like I need to define the triggers a little better.

Instead of the trigger 'starts to cast a spell' it could be 'starts to speak.'
Instead of the trigger 'the dragon tries to breath fire on us' it could be ' the dragon opens its mouth in front of us.'

Adds a little dramatic tension as maybe the wizard or dragon are just try to talk to the players.

There seems to be little argument over triggers regarding movement. So far the general consensus is the Trigger fires after the target moves 5 feet.

 

[UngeheuerLich]

When your trigger arise, you either take your readied action or you don't. If you Readied an Action to such trigger, when the rogue run you either shoot him or you don't. The risk of doing or not doing so is a case by case for sure.

Of course. But if you don't shoot and the rogue still runs your action is wasted... so be sure what part of running away triggers your readied action

 

[Plaguescarred]

FWIW There's some Sage Advice on Ready an Action timing regarding spellcasting


Can you ready dispel magic to stop another spell from taking effect? The easiest way to stop a spell is to castcounterspell on its caster while it’s being cast. If successful, counterspell interrupts the other spell’s casting, and that spell fails to take effect. Counterspell works against any spell, regardless of a spell’s casting time or duration.
With the Ready action, dispel magic can be cast in response to another spell being cast, yet dispel magic can’t substitute for counterspell. The main reason is that dispel magic removes a spell that is already on a target, whether that target is a creature, an object, or some other phenomenon. Dispel magic can’t pre-dispel something. If a spell isn’t already present on a target, dispel magic does nothing to that target. The best that a readied dispel magic can do is dispel a spell immediately after it’s been cast to prevent it from having any effect after the action used to cast it. For example, on your turn you could say something like this: “I ready dispel magic, and if the high priest casts a spell on anyone, I cast dispel magic on the target if the spell takes hold.” If the high priest then cast hold person on your companion who fails the save against it, you could unleash your readied dispel magic and end hold person.

 

[morikahn]

FWIW There's some Sage Advice on Ready an Action timing regarding spellcasting ...

I've familiar with this Sage Advice; there are a couple others involving the Ready action. This response is really about the effect of Dispel Magic more than spell timing. Its saying there is no point in casting the Dispel Magic before an opponent has cast a spell as there is nothing to dispel.

 

[Morrus]

The trigger for a readied action doesn't have to be an action; it can be an event. The text says "perceivable circumstance", not "action".

So "when the rogue leaves that square" is a trigger. It goes off when the rogue leaves his square. As long as it is a circumstance, and you can perceive to, it is a valid trigger (subject to DM approval, as always).

The example in the book is a goblin stepping on a trapdoor - presumably partway through its move.

 

[Plaguescarred]

I've familiar with this Sage Advice; there are a couple others involving the Ready action. This response is really about the effect of Dispel Magic more than spell timing. Its saying there is no point in casting the Dispel Magic before an opponent has cast a spell as there is nothing to dispel.

Well it clarify you can use a readied action before a spell is cast when the trigger is for casting a spell.