[RPG] Shield Master – Does the reaction to block a Fireball happen before or after the Dexterity saving throw

dnd-5efeatsreactionssaving-throwshield

The Shield Master feat (PH p.170) grants the following ability:

  • If you are subjected to an effect that allows you to make a Dexterity saving throw to take only half damage, you can use your reaction to take no damage if you succeed on the saving throw, interposing your shield between yourself and the source of the effect.

Does the player decide to expend their reaction before they roll the saving throw, or after?

Best Answer

The language is thoroughly ambiguous. It can be interpreted in either of two ways:

  • (you can use your reaction to take no damage) (if you succeed on the saving throw)

    If you succeed on the saving throw, you can use your reaction to take no damage.

  • (you can use your reaction) (to take no damage if you succeed on the saving throw)

    You can use your reaction to set up a delayed trigger to take no damage on a successful saving throw.

The main question being whether "if you succeed on the saving throw" is part of the effect, or a further condition on the reaction.

There is plenty you can infer here. For example:

  • If they intended "if you succeed on the saving throw" to be part of the condition, they could have grouped it with the other condition and come up with something much clearer: "If you [must make a Dexterity saving throw to take half damage], and you succeed on the saving throw, you can use your reaction to..."

    Since they didn't use this wording, clearly they must mean for the reaction to be used before the save is rolled...

On the other hand...

  • There are other effects which explicitly state they must be used before a result is known/rolled/etc.

    Since they didn't explicitly state that you need to use your reaction before knowing the result of the save, clearly they must mean for the reaction to be used after the save is rolled...

Ultimately, the choice is your DM's. Or Jeremy Crawford's, if he gets around to providing a Word of God answer.

(insert rant about sloppy templating)

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