[RPG] How much information should the defender have when deciding whether or not to cast Shield


I'm playing a 5e campaign as a Fighter, planning on becoming an Eldritch Knight.

Thus far (we're still level 1), the DM has been resolving attack rolls against us by telling us the result of the attack roll, and asking us if it hits:

  • DM: "The goblin takes a swing at you!" (rolls behind DM screen) "Does a 19 hit you?"
  • Player: (looks at character sheet) "Yep. Ouch!"

This has worked fine so far, since there isn't really anything any of our characters can do about being attacked, and you can't derive very much useful information from knowing what a monster's modified attack roll was. However, in a couple levels, I'm going to learn to cast spells, specifically the shield spell, which changes things a bit.

I know that I don't have to declare whether or not I cast shield until I know whether the attack would hit me, but am I supposed to know the exact modified attack roll result when I decide? Or should the sequence of events be more like:

  • DM: "The goblin takes a swing at you!" (rolls behind DM screen) "What's your AC?"
  • Player: (looks at character sheet) "It's 16."
  • DM: "Okay, the attack hits."
  • Player: "I cast shield in an attempt to protect myself, raising my AC to 21. Does it still hit me?"
  • DM: "Nope, it glances off your magical barrier."

This is important because if I know the attack roll result, I know whether it's worth bothering to cast shield, whereas if it's hidden from me, I have to guess whether the attack beat my AC by 5 or more.

Best Answer

According to this tweet by Mike Mearls, you're supposed to know with certainty whether the shield is enough to protect you or not, so that you can't waste the spell, unless you choose to:

Querent: Am I right..Wiz should know roll before using Shield,cant 'waste it' from not knowing roll?

Mike Mearls: correct

This is also how I have seen it be done in every game I have played. The DM announces the attack score, and the player compares it to their AC and announces if it hits or not.