[RPG] When an invisible character leaves a blindsight creature’s reach, does the creature get an Opportunity Attack

dnd-5einvisibilityopportunity-attackspecial-sensesvision-and-light

A character in the party cast Invisibility on herself, making her invisible. She then tried to move past a Giant Spider, which has Blindsight 10 ft. Per "Does Blindsight detect Invisibility?" the Spider can still tell that the character was there, since the rules for Blindsight say "A monster with blindsight can perceive its surroundings without relying on sight"

But, as she leaves the Spider's reach, does the Spider get an Opportunity Attack? Per the rules, "You can make an opportunity attack when a hostile creature that you can see moves out of your reach."

Blindsight just says "can perceive", but an Opportunity Attack requires "you can see". Is the "perceiving" of Blindsight enough to be able to "see" for the purposes of the Opportunity Attack rule?

As the DM, I ruled "no" simply on the principle that "When in doubt, rule in favor of the players", but I'm really not sure that's right, as I may be taking things too literally.

Best Answer

Yes, they'd get an Opportunity Attack

Your citation on Opportunity attack requiring a 'creature you can see' does imply sight, but that's a much too literal approach to the answer.

A clarification on blindsight and stealth from Jeremy Crawford on Twitter suggests that blindsight allows you to spot a creature - and would thus trigger the opportunity attack. Note: The invisible creature can choose to attempt to Hide - which would prevent the OA.

Blindsight lets you spot an invisible creature in range, but that creature can still try to hide behind something with Stealth.

While ruling in favor of your PCs is a good idea - there may be times when the opposite could occur (a PC with blindsight wanting an OA.) In this case, the blindsight creature knows exactly where the PC is and that they're leaving - which would trigger the Opportunity Attack.

Yes, if the second Goblin is not within the Reach of the thing making the opportunity attack

It seems a bit weird, however the criteria for triggering an opportunity attack are:

You are moving out of the reach of a hostile creature
This movement is from one of your Actions, Bonus Actions, Movement or Reaction
You have not taken the Disengage action
You are not Teleporting

For this question we can discount Point 4, as the Goblin Boss can't teleport.

We'll also ignore Disengaging for now.

For Point 2, the movement is by the Goblin Boss' Reaction, which fulfills that criteria

For Point 1, if the swapping with the second Goblin does not cause the Goblin Boss to leave the Reach of any hostile creature, it will not trigger an Opportunity attack. In the diagrams below, the first set of movement will not trigger an opportunity attack, while the second set will.

EG    ->    EB
B           G


EBG   ->    EGB

E - Enemy; 
G - Goblin; 
B - Goblin Boss

Note that wherever the second Goblin is moved from, it does not trigger an Opportunity attack from anything as its movement is forced by the Goblin Boss.

As for using Disengage (via Nimble Escape), it only stops OAs for the rest of your Turn, not the entire Round.

So, if someone had Readied an action to hit the Goblin Boss when the Boss did a specific thing, then the Goblin Boss did that thing on the Boss' turn, and in Reaction the Boss used Redirect Attack, that would not trigger an OA, wherever it moved, as it is still the Boss' Turn so Disengage is still in effect. But normally, Disengage would not help for this.

[RPG] How does this change to the opportunity attack rule impact combat

This is going to make your combats a lot more static. Nobody likes taking opportunity attacks, and it costs an action to get away without one (rogue aside), so everyone who likes melee will tend to get into position and then stand very still -- even being in a poor tactical position would be better than taking OAs or giving up a turn to change it.

A big consequence of this is that any abilities that depend on precise positioning are much less useful. For example, the Protection fighting style depends on being adjacent to a friend, and this rule will make it more difficult to set that up, so you should probably go with a different style instead. Similarly, close range spells like thunderwave may be more difficult to use effectively, because your allies will have less ability to move away without taking OAs for doing it.

Conversely, effects that prevent reactions (such as the shocking grasp cantrip) become stronger, since they effectively remove the ability to make OAs and thus free up melee characters for movement. This includes conditions like incapacitated, stunned, or paralyzed.

It won't change things much for your range-focused combatants, who generally just want to get away if they find themselves in melee and will therefore take OAs anyway.

What you're describing is a throwback to 3rd edition, only without the five-foot step to help ameliorate the problems it causes. The 5-foot step was awkward and weird, but still better than effectively locking everyone in place once they engage in melee.

Best Answer

Yes, they'd get an Opportunity Attack

Related Solutions

[RPG] Does the Goblin Boss’s Redirect Attack provoke an opportunity attack

Yes, if the second Goblin is not within the Reach of the thing making the opportunity attack

[RPG] How does this change to the opportunity attack rule impact combat

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