Based on this question (Can the sleep spell wake me up?) I had a question about the mechanics of the sleep spell. I don't currently play D&D, so I'm not too familiar with the rules. However, I read the text of the spell here. It is a ranged enchantment with a duration of one minute. Since the spell has a duration rather than occurring instantaneously, I was wondering what happens if a creature moves into the range while it is active, or if a creature that was previously ignored by the spell (such as an unconscious creature) becomes eligible for the effects before the end of the spell.

My guess was that it would affect the creature normally (assuming the spell hasn't already put to sleep enough creatures to reach the HP limit) but when I asked about it in the comments I encountered some different opinions. What is the best way to interpret this spell? Are there any general principles that I'm unaware of?

Thinking about it, I guess the other way of interpreting it would be to say that "Creatures within 20 feet of a point you choose within range are affected" has an implicit time constraint that they have to be in range at the moment the point is chosen. So it seems like the mechanics of ranged spells are important here.

This just made me think of another related question, which I think is close enough to also ask here: what happens if a creature that was in range at the start, and put to sleep, is moved out of range before the end of the spell?

  • \$\begingroup\$ This is a very interesting question (tbh I'm a little surprised at the lack of support). Instinctively (and probably influenced by my recollection of the spell in previous editions): I assumed the duration referred to how long the affected targets remained sleeping but the affected creatures had to be determined at time of casting. However, I have not yet been able to find anything concrete to confirm this. \$\endgroup\$ Commented Apr 6, 2016 at 22:29
  • \$\begingroup\$ (cont.) Presumably, if the intent had been as I believe, any potential confusion could have been trivially avoided by making the spell instantaneous and specifying sleeping time in text. However, that would then also make it impossible to Dispel the effect. I do also have a concern that your interpretation makes it trivial to create a "sleeping trap". If that were intended, I would expect the text of the spell to make specific mention of creatures moving into the affected area. And then what would happen if a creature lost some HP while within the area? \$\endgroup\$ Commented Apr 6, 2016 at 22:37
  • \$\begingroup\$ @CraigYoung: Oh, I hadn't thought about what happens if a creature loses HP. It does seem to me now that if it was supposed to work the way I originally thought, it would say something about creatures moving into the area being affected. \$\endgroup\$
    – coffee
    Commented Apr 6, 2016 at 22:52

3 Answers 3


As a general rule, unless otherwise indicated in the spell description, the targets must be within range at the time the spell is cast (and Sleep doesn't say otherwise).

The duration of the Sleep spell is how long the affected creatures will remain asleep if they are not woken by other means.

Once asleep, they can be moved to any distance without breaking the spell (as long as the movement itself is not rough enough to wake them).


Interesting question.

As we know, D&D works on the premise that specifics beat general.

The general rules for spell targeting state the following (under Casting a spell - Range) :

The target of a spell must be within the spell's range. (Player's Handbook, p. 202)

Since no specifics are given in the description of Sleep (other than the number of hit points affected), one could assume the targets have to be in the original range to be affected.

Some spells worth mentioning

Color spray
Like Sleep, Color spray affects a number of hit points. While it only has a 1 round duration, the spell doesn't state if a creature moving into the area of effect before the end of the round would be affected (assuming their hit points are lower that the remaining pool of the spell). In absence of specifics, we have to consider it wouldn't.

Faerie fire
On the other hand, Faerie fire (even if poorly worded) specifically targets "Any creature in the area when the spell is cast (PHB, p. 239)", which is a major addition, considering the question asked here. Thus, no one entering the zone after the casting would be affected (as in the quote above). But why bother mentionning in the description if it's already covered by the general rules?

Inconsistencies in the spells descriptions? Oversight? Should the wording of Sleep have included the "when the spell is cast" part, as seen in Faerie fire?

Maybe. But it didn't. Hence the question.

As a DM, I would definitively limit the effects to the creatures being in range of the spell when it was cast (unless the description says otherwise).

Moving sleeping creatures out of range

To adress your second question, here's what the rules say :

Once a spell is cast, its effects aren't limited by it's range, unless the spell's description says otherwise. (Player's Handbook, p. 203)

Since nothing specific in the description of Sleep (other that the "shake or slap to awake" clause) invalidates that general rule, we can safely assume that carefully transported, magically asleep creatures wouldn't wake up from being further from the caster than the spell's range. The same logic applies to a lot of spells (Bless, Heat metal, etc.).


For your first question I think you are confusing duration with cast time a bit. A way to think about it is kind of like you are casting an acid cloud, the cloud dissipates quickly but anything the acid landed on would have to deal with the effects for longer even if they move about.

A more RAW answer is to consider that the spell does not say that the putting to sleep last until the spell ends, just the effect of being put to sleep last until the spell ends. I would like it to be a bit more clear, as normally the spells I have looked at would give an explicit what to do if someone enters a zone after the spell starts (I think, my memory for exact text is poor).

For the second question the end conditions of the magical slumber are pretty specific:

falls unconscious until the spell ends, the sleeper takes damage, or someone uses an action to shake or slap the sleeper awake.

Whether moving someone counts as shaking them I would guess depends on the GM and the mover's intentions. Though normally I just tie people up at this point.

  • \$\begingroup\$ No, there's nothing to suggest OP is confusing duration and casting time. It might help if you refer back to the linked question to understand the origin of this question. It's a question of whether more targets can become affected if other constraints have not yet been met. \$\endgroup\$ Commented Apr 6, 2016 at 22:50
  • \$\begingroup\$ I am having trouble with understanding duration in a way. I thought that the spell would continue affecting new creatures for the entire duration, but this may not necessarily be true. So I might have misunderstood what "duration" means exactly. \$\endgroup\$
    – coffee
    Commented Apr 6, 2016 at 22:54

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