William the Wizard is under the effects of the Slow spell, which states:

If the creature attempts to cast a spell with a casting time of 1 action, roll a d20. On an 11 or higher, the spell doesn't take effect until the creature's next turn, and the creature must use its action on that turn to complete the spell. If it can't, the spell is wasted.

On its turn, he casts Acid Splash on Wanda the Warlock. The creature concentrating on Slow rolls 11+, which means Acid Splash doesn't go off until next turn. Before that happens, Wanda uses her turn to move behind a wall, fully obstructing her.

The Acid Splash spell requires line of sight:

You hurl a bubble of acid. Choose one or two creatures you can see within range. [...]

Also, the basic rules state that the spell would require a clear path:

To target something, you must have a clear path to it, so it can't be behind total cover.

Can William complete his spell that targets Wanda, who is now out of sight?

  • \$\begingroup\$ The "ready a spell" action could likely give another flavor of this question with the same answers (or lack thereof). \$\endgroup\$
    – aschepler
    Commented Jan 6, 2020 at 17:25
  • \$\begingroup\$ Not a duplicate, but extremely close: rpg.stackexchange.com/q/133379/2788 \$\endgroup\$ Commented Jan 6, 2020 at 17:32

3 Answers 3


To start with, I'll point out that this scenario is extremely similar to a mage having readied a spell, and then releasing it on the next turn. In both cases, the casting occurs during the first turn, and the effect occurs during the second.

For anyone who considers these scenarios identical, then one should just apply the same logic used for readied spells. And this is answered here: Can a spell be readied to trigger when its intended target comes into view?. That is, the target of the spell is not even determined during casting at all. Thus, there's no such thing as "a target that moves out of sight". The target's not a target until the second turn, and the spell works completely normally, regardless of whatever movement might have occurred by any potential targets prior to release of the spell's effect.

This interpretation is, as noted in that answer, loosely supported by this reply on Sage Advice:

For readying a spell or other action, does the target have to be in range? Your target must be within range when you take a readied action, not when you first ready it.

Note that the conclusion derived from that answer, for the other RPG.SE answer, is not directly stated. It's inferred as a natural consequence of that more general rule. But it does seem reasonable.

That said, it is just an inference and the rules don't provide exact guidance. So, assuming one does not consider the effect of Slow to be identical to a readied spell, or if one does not agree with the RPG.SE answer regarding readied spells and targeting, then we have to go further in our analysis. Read on… :)

Can William complete his spell that targets Wanda, who is now out of sight?

Yes, no problem there. They cast the spell using their first action and nothing changes after that that would prevent the spell from being completed. But, the effect of the spell fails to hit Wanda. This introduces the question as to what that effect actually is.

As I see it, there are two options:

  • The bubble of acid follows the target
  • The bubble of acid lands where originally intended

The latter option is simpler to use, but the former is supportable because, well…it's magic.

From the spell description:

You hurl a bubble of acid

You can cast the spell, no problem. That happens right away. But being slowed, the effect of the spell is delayed. And the effect of the spell is that "You hurl a bubble of acid".

If one has ruled that the bubble follows the target, then by the time you actually do that (using your action in your next turn), the target has obtained full cover. You hurl the bubble of acid toward the target, but they are protected by the cover, which is what your bubble of acid winds up hitting.

Depending on what the cover is, that may or may not have any further interesting effect (a stone wall might get slightly marred, but would otherwise be fine).

If one has ruled that the bubble lands where originally targeted, then it still lands there. If the target has moved behind cover by that time, they are protected. (I'd note however that if they just move 5', still within the range of a two-targeted splash, then if the cover is only between them and the caster, rather than between them and the originally targeted location, they'd still take damage under this interpretation.)

Nicely, the rules as written also fit the narrative. You're slow. It is not surprising that your targets may be able to take advantage of that slowness, by ducking, hiding, or otherwise avoiding your attacks.

It's not quite "bullet time", but it's the same basic idea. Your targets' reflexes have essentially been enhanced, relative to your own.

Additional considerations:

What happens when there are two targets?

Under one interpretation above, the direction of the cast bubble should change as the targets move. If there are two targets, then what? If neither target moved, then the bubble would land between them, splashing them both. It's thus reasonable to rule that should either move away from the other, the bubble will land between them, potentially splashing neither depending on where they moved (i.e more than 5' away from each other).

Under the other interpretation, the movement of the target or targets is irrelevant (and so it's easier to decide what happens).

What happens if the target (or targets) moves, but not into cover?

I think the answer to this can be inferred from all of the above. But it's worth noting that the direction of the bubble may or may not change after casting, depending on how one rules (either is valid, according to what's written). If one rules that it does, then if there's only one target, they will get hit if they don't achieve cover with their movement. If there are two targets, neither might be hit, depending on whether the location between them is too far from either to have any effect.

However, taking the main point above with the two-target scenario, we can see that if one is ruling that the direction of the bubble is not changed after the spell is cast, then if one or the other of two targets move before the effect occurs, the bubble might still hit one or the other of the targets, depending on whether they have moved far enough from the originally targeted location (since that's where the bubble will land, under that interpretation). Likewise a single target would be hit only if they remain close enough to the original location. They could avoid the bubble entirely even without achieving cover.

To sum up: the rules don't provide explicit guidance about whether the direction of the acid bubble changes after casting, so there will have to be a ruling determining that. Once that has been decided, it's possible to completely understand how the spell works under the effect of Slow.

  • \$\begingroup\$ "A target with total cover can't be targeted directly by an attack or a spell, although some spells can reach such a target by including it in an area of effect." They've already been targeted though. There's no attack or skill check associated either, so your can't grant them bonuses to avoid damage. \$\endgroup\$ Commented Jan 7, 2020 at 3:17
  • 1
    \$\begingroup\$ @Pureferret Yes you can, just have it hit the wall, no damage. \$\endgroup\$ Commented Jan 7, 2020 at 8:26
  • \$\begingroup\$ I like your answer since hitting the wall does make the most sense, even if it makes the Slow spell (in my opinion) very overpowered. Bonus question: Acid Splash also allows targeting up to two creatures standing within 5 feet from each other. What happens when the two targets move away from each other before 'completing the spell'? \$\endgroup\$
    – Cypher
    Commented Jan 7, 2020 at 10:36
  • 1
    \$\begingroup\$ @Cypher slow had better be powerful considering it gives a save every round, and a wisdom save at that. \$\endgroup\$
    – John
    Commented Jan 7, 2020 at 14:10
  • \$\begingroup\$ @PeterDuniho Thank you for your thoughts! In the end, I guess there is no obvious RAW solution, so I'll have to do some rulings of my own. \$\endgroup\$
    – Cypher
    Commented Jan 8, 2020 at 8:37

Wanda is a valid target, only the effect is delayed

William has a clear path to Wanda, so they are a valid target for spells. Wanda is within sight so they are a valid target for Acid Splash.

Suppose William rolls an 11 and so:

the spell doesn't take effect until the creature's next turn

The next turn Wanda is out of sight and there is no clear path to them.

But that doesn't actually matter. Wanda has already been "chosen" as the target, they have already been "targeted". Only the "effect" has been delayed.

But I think that's dumb

The rules are clear. Wanda will be hit by the acid splash despite being fully obstructed by the wall. Were they hit some time within those 6 seconds that they were moving? I guess so. But that doesn't feel very good to me.

I would rule that if the target is no longer valid, then the spell is cancelled. It's a lot cooler to duck behind a wall against a slowed foe. Just be aware that this would be a huge buff to the slow spell!

  • \$\begingroup\$ Thank you for answering, my thought process was pretty much the same. Having the spell still go off feels the closest to RAW, but I have no idea how to describe it in game (I'm the DM for our group). Does the acid bubble follow Wanda around the corner? What if Wanda goes to another room and closes the door behind her? It just feels there is no good way to have it make sense, so I would prefer to just cancel the spell. But as you said, this feels like a huge buff to an already powerful AoE spell. \$\endgroup\$
    – Cypher
    Commented Jan 6, 2020 at 9:16
  • 5
    \$\begingroup\$ "Does the acid bubble follow Wanda around the corner?" - HEAT SEEKING ACID BUBBLES!!!! What if Wanda goes to another room and closes the door behind her? - Plane shifting acid bubbles!!!!! \$\endgroup\$
    – Thatguy
    Commented Jan 6, 2020 at 10:16
  • 2
    \$\begingroup\$ Wouldn't the part from Slow that says the "creature must use its action on that turn to complete the spell. If it can't, the spell is wasted." mean it won't work? I think it's the only instance of "completing" a spell, but wouldn't that mean that creature would need to satisfy the same conditions for casting the spell as when they started to cast it? Because if they need to complete the spell that means it hasn't been fully cast yet. \$\endgroup\$
    – RallozarX
    Commented Jan 6, 2020 at 13:19
  • 1
    \$\begingroup\$ @RallozarX Exactly: The problem is, nothing explicitly says what "completing a spell" means or what's necessary for it to happen. \$\endgroup\$
    – aschepler
    Commented Jan 6, 2020 at 17:23
  • 1
    \$\begingroup\$ @jgn There are spells that take 1 minute to cast, or even 1 hour. Are you claiming that RAW states, if you cast them when there is a valid target, and 1 minute later the target is gone, they still go off? Please [cite]. \$\endgroup\$
    – Yakk
    Commented Jan 6, 2020 at 22:11

According to this answer the rule that Jeremy Crawford has put out via his twitter, for a similar albeit distinct, scenario is that in general a spells effect is suppressed if the target becomes invalid.

There's no rule governing what happens when a valid spell target temporarily becomes an invalid target. A good rule of thumb is that the spell is suppressed while the target is invalid.

(Emphasis carried over)

The distinction is that this example only references spells with a non-instantaneous duration. I would surmise that if a target becomes invalid between being targeted and the (delayed) effect triggering, if the duration is instantaneous, the spell fizzles and the spell slot is wasted. Perhaps a DM could rule that the spell slot isn't, but the spell still does not work.

Bear in mind that this doesn't necessarily mean that slow is now overpowered. You've forced an enemy into cover, which can lead to it's own advantages.


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .