Our party entered a seemingly empty room. My PC correctly assumed invisible opponents to be in the room, so he readied an action: "If I am attacked, I strike the attacker." Then an opponent attacked him, becoming visible.

Is the PC entitled to attacking the opponent before the opponent's attack strikes home?

The rules seem to imply this:

The action occurs just before the action that triggers it [emphasis mine]. If the triggered action is part of another character’s activities, you interrupt the other character. Assuming he is still capable of doing so, he continues his actions once you complete your readied action. (PHB, p. 160)

My logical problem is that the attacker becomes visible only by attacking the PC.

The readied action interrupts the attack: The attacker has only declared the attack but not actually attacked the PC, he could even be killed without finishing his attack. In that case: Why would he become visible?


1 Answer 1

  • If combat hasn't started, your PC can't ready an action. Actions can't be readied when not in combat; this is discussed at length in the Dungeon Master's Guide (25–6).
  • If the DM said, "Roll initiative," your PC can, on your PC's turn, ready an action. However, readying an action doesn't give your PC any senses that your PC doesn't already possess. Unlike, for example, the trigger of the spell contingency, your PC's readied action can't be triggered by a stimulus your PC isn't aware of.

In this case, your PC's readied action would trigger, but it would trigger only after the attack roll determined if the invisible foe's attack hit and dealt damage or missed. The ready action I attack the creature is fine, but the trigger When I'm attacked tries to interrupt a process that resists interruption. That is, your PC can't take an action that's predicated upon the foe finishing its action before the foe finishes its action.

Unlike movement or casting a spell, making an attack roll is a one-step process, occurring all at once. The Player's Handbook on Attack Roll says

An attack roll represents your attempt to strike your opponent on your turn in a round. When you make an attack roll, you roll a d20 and add your attack bonus. (Other modifiers may also apply to this roll.) If your result equals or beats the target’s Armor Class, you hit and deal damage. (134)

A creature that's affected by an effect like the typical invisibility spell does not give the defender a window in which to take actions in the quantum time between the creature becoming visible because it made an attack roll and the result of the creature's attack roll still being unknown. The creature's invisible while it's making that attack, it makes that attack by making an attack roll, and that attack roll's result determines if the attack hits and deals damage or misses. (Were this not the case, folks wouldn't suffer any penalties for being attacked by invisible attackers—if a typical invisible creature became visible upon, for instance, making the attack roll but before the attack roll's outcome is determined, the attacker would be visible when the outcome is determined, negating the advantage invisibility typically provides!)

So, yeah, as the defender in this situation, your PC is going to have to learn the result of the invisible attacker's attack roll the hard way—when the attacker's invisibility effect ends because the attacker either dealt damage to your PC or the attacker's attack missed the PC. Only then will your PC's readied action's trigger will be pulled, and your PC can attack.

To be clear, as a benefit of your PC having readied rather than delayed, after the invisible foe's attack is resolved and the foe's visible, this DM would put your PC ahead of the formerly-invisible foe in the initiative order, resolve your PC's readied action, then finish the formerly-invisible attacker's turn. Had your PC simply delayed—your PC wanting to make a full attack if the invisible foe reveals itself, for instance—, then your PC would end up in the initiative order behind the foe. Whether this is small consolation or shifts the tide of battle depends mightily on the circumstances.

  • \$\begingroup\$ In our case initiative had already been determined as we had fought some other opponents right outside the room, so readying was perfectly legal. \$\endgroup\$
    – Giorin
    Commented Feb 19, 2019 at 8:29
  • \$\begingroup\$ I am still reflecting on your answer. Your points are perfectly logical, but the problem with "ready an action" is that it is not entirely logical concerning sequences. I edited the rules quote into my question to point this out: The action takes place "just before the action that triggers it". This is some kind of rules time-travel-paradox and while I can follow your logic, I do not think it is entirely consistent with this wording. \$\endgroup\$
    – Giorin
    Commented Feb 19, 2019 at 8:47
  • \$\begingroup\$ @Giorin Inconsistency, thy name is the ready action! Seriously, if you've another way to adjudicate this, I'd be absolutely thrilled to hear it! I've read, written, and thought a lot about the ready action—here, for example—, and the only solid conclusion I've reached is, "Expect table variation." (And, on the first comment, if it's okay with you, I'll keep the "No ready outside combat" bullet in the answer because it may be important for other readers.) \$\endgroup\$ Commented Feb 19, 2019 at 11:49
  • \$\begingroup\$ @Giorin (Note that a similar situation occurs whenever a ready action is Attack a creature and the trigger is When I can. Strictly, the attack would occur before it could be made… which is not just impossible but nonsense. It's why I included in this answer the bit about changing the initiative order based on the ready action instead of trying to force-wrap anyone's head around the ugly logical inconsistency. Changing the initiative order represents having taken the action, essentially, before the trigger could be pulled rather than having it be literally so.) \$\endgroup\$ Commented Feb 19, 2019 at 14:15
  • \$\begingroup\$ As said previously your logic is compelling. The only alternative I see is far less convincing, though it fits better with the wording: You could say the readied action has to strike the still invisible attacker with 50% miss chance. I admit that if you think about the logic of this action you get crazy, (You suddenly know where to strike as the opponent is about to become visible.) But at least the opponent does not get visible for something he did not yet do. \$\endgroup\$
    – Giorin
    Commented Feb 21, 2019 at 21:34

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