Can the Shield spell be cast in response to being hit by an invisible enemy?

Question

Let's say I have a PC with the shield spell. I'm not surprised, and an invisible enemy hits me with an attack. My DM has not yet told me the attack roll number, so I am in a position to cast shield if I choose to.

However, the enemy is invisible, so would I be able to cast shield in response to an attacker I can't see? Let's assume the attacker is permanently invisible, like they're using the greater invisibility spell. On the one hand, the shield spell simply says:

1 Reaction*
* - which you take when you are hit by an attack or targeted by the magic missile spell

There's no mention of needing to see the creature.

On the other hand, it seems wrong to me that I can react to an attack I can't see coming.

Are there any rules I've missed that would prevent the shield spell from being cast in this scenario?

Answer 1

The shield spell can be cast after you know you are hit by an attack

Though the specifics of how the shield spell actually plays out varies table-to-table the spell states that the reaction is taken (emphasis mine):

[...] when you are hit by an attack [...]

It does not occur when you are targeted, or when an attack roll is made; it occurs when you are actually hit. Once the attack roll has already beat out your AC. You could explain this by saying shield involves time travel or perhaps your caster is waiting to know whether the attack would hit them. Some sort of interpretation is required here if you want the spell to actually make sense.

Personally, I say it's just magic and for some reason the caster can use this after they are hit but it can also prevent that same hit. This is similar to absorb elements granting resistance to the triggering attack as well.

The shield spell does not require you to see your attacker

The spell is already doing some extraordinary things and looking at the description, the spell does not state that you need to see the attacker and so you do not need to see them.

So you can cast shield even after being hit by and invisible attacker and that same hit can be turned into a miss.

---

Examples of the oddities/interactions of the shield spell or similar questions

• How much information should the defender have when deciding whether or not to cast Shield?
• Does blocking an attack with the Shield spell still trigger Armor of Agathys?
• Can the Shield spell be used against Shocking Grasp?
• When the Shocking Grasp cantrip hits, can it trigger the Tempest cleric's Wrath of the Storm reaction?
• Can a Precision Attack be added to an attack roll after an enemy uses Shield as a reaction to that attack roll?
• Are getting hit and taking damage simultaneous events?

Many of those questions have competing answers; there's a lot of confusing bits and oddities to the shield spell. As such, in my opinion, many of its effects and interactions are best left to the GM.