Multiattack defense vs legendary actions

Question

I have a question about the DnD 5E Ranger Hunter Multiattack Defense feature.

Should you or do you get Multiattack Defense against legendary actions? For example, when you get a bite and two claw attacks from a dragon you obviously get Multiattack Defense if one of those hits and when the dragon ends its turn you go back to normal AC.

However, as the players in the round take their turns, the dragon can use its legendary action points to tail strike you every single turn until it runs out of legendary action points. So the real question is, the PHB reads that you would have normal AC for every legendary action since it's a new turn, but the designed intention of the feat makes me think you should have +4 AC. Has this been answered by a developer?

Answer 1

Multiattack Defense only helps against legendary actions with multiple attacks

The ranger's Hunter archetype Multiattack Defense feature states:

When a creature hits you with an attack, you gain a +4 bonus to AC against all subsequent attacks made by that creature for the rest of the turn.

The text for legendary actions states

A legendary creature can take a certain number of special actions--called legendary actions--outside its turn. Only one legendary action option can be used at a time and only at the end of another creature's turn.

If the dragon hit you on its turn triggering Multiattack Defense, the first time it will be able to attack you again with a legendary action will be outside its turn, that is, not during the turn where it hit you. The Multiattack Defense it triggered during its turn does not apply any more.

The end of a creature's turn is part of that creature's turn. The legendary attack does not happen on the dragon's turn, but it happens on the character's turn.

There are actually a few select monsters that have multiple attack options with their legendary action, for example Eberron's Sul Katesh can make multiple attacks with her arcane blast, Jarlaxle Baenre can make multiple attacks with his daggers, and a Giff Warlord from Boo's Astral Menagerie can make two morningstar attacks. If one of them attacked you at the end of your or another character's turn, and hit you with the first attack, this would trigger Multiattack Defense for the subsequent attacks.

For the dragon however, which only can make a single attack with its legendary actions, it will not do you any good.

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P.S. A possible exception is if the dragon hit you with an attack on a turn that is not its own, for example it could have had a readied action to bite anybody who comes into reach, or it could bite you as you move out of its reach as an opportunity attack. In those cases, it could successfully bite you, and then at the end of that same turn, as it is not its turn, hit you with a legendary attack. Since that would still be the same turn, your Multiattack Defense would kick in here. (Thanks to @MJD to point out the corner case).

Answer 2

Technically, Multiattack Defense doesn’t trigger on Legendary Actions ever.

Multiattack defense states:

Multiattack Defense

When a creature hits you with an attack, you gain a +4 bonus to AC against all subsequent attacks made by that creature for the rest of the turn.

I have emphasized “rest of the turn” because Legendary Actions occur between turns, not on a turn:

A legendary creature can take a certain number of special actions — called legendary actions — outside its turn. Only one legendary action option can be used at a time and only at the end of another creature’s turn.

Since Legendary Actions occur between turns, there is no “rest of the turn” where you would have the +4 AC.

However, it makes sense to let it work anyway on Legendary Actions that feature multiple attacks per single action.

This is obviously (at least to me) just a bug in the rules, so to speak, caused by the weirdness of Legendary Actions occurring between turns. It makes much more sense to allow Multiattack Defense to work against a Legendary Action involving multiple attacks.

Either way, Multiattack Defense would not trigger against multiple, single attack Legendary Actions.

Multiattack Defense is designed to work against the subsequent attacks of an action involving multiple attacks. If a Legendary Action only includes one attack, Multiattack Defense never triggers. As you observe, if the dragon uses another Legendary Action at the end of a later turn, it is a new turn, and once again, Multiattack Defense does not trigger.