Are there any RAW effects or attributes that give resistance to the Sleep spell?

Question

The Sleep spell states:

This spell sends creatures into a magical slumber. Roll 5d8; the total is how many hit points of creatures this spell can affect.

(PHB 276)

The sleep spell doesn't deal damage directly, instead affecting a number of hit points (current hit points) and sending one or a number of creatures into magical slumber. Since this spell does not deal direct damage, I don't believe there are any attributes, spells, or effects that can counter the Sleep spell's effects, aside from the one caveat at the end of the spell description:

Undead and creatures immune to being charmed aren't affected by this spell.

This, however, simply immunizes the creature from the effects of the spell entirely. I'd like to find a trait, spell, or other effect that is RAW and that lessens but does not necessarily entirely nullify the effects of the Sleep spell and other spells that affect hit point totals (e.g. Color Spray).

My motivation? I have a homebrew race that I'm developing for my campaign, and one of its defining characteristics is resistance to anything and everything magical (broken, but it fits the story). I've already given it resistance to all types of magical damage (except for force damage; I've made a racial feat for that) and the trait Magic Resistance. Primarily I'm using members of this race as enemy NPCs. I understand that a race like this is beyond overpowered, but that is the topic for another discussion.

As of now, this race is not resistant to the effects of spells that affect hit point totals. I'd like to find a way to mitigate the effect this category of spell has on this race without making it entirely immune.

RAW answers only, please, if they exist.

Answer 1

Elf's Fey Ancestry is the closest I can think, but it is still immunity, not "resistance".

Fey Ancestry. You have advantage on saving throws against being charmed, and magic can’t put you to sleep.

"Resistance"

Aside from that, "Resistance" against sleep is something hard to define, to begin with. It is not a damaging spell, so the common "resistance" = half damage doesn't apply.

It also doesn't require an Attack Roll or a Saving Throw, so disadvantage/advantage (respectively) also doesn't apply.

Because of these reasons, I don't think there is any kind of feature that mitigates the sleep spell - every entry I know of is either immune to it or not.

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Little Frame Challenge: You want it RAW, but you are yourself using it for a homebrew, so I fail to see the relevance of RAW.

A simple feature that is somehow "equivalent" to Resistance would say something on the lines of

Putting this creature to sleep costs twice from the HP pool.

Answer 2

Resistance protects vs damage; advantage on saving throws fits your need

Sleep does not do damage. There typically isn't a save versus the Sleep spell, so resistance is an odd attempt at a mechanical fit. However, there is some room to work here by way of a RAW example.

You will want to give your monster advantage on saving throws versus sleep in your homebrew. That mechanic is consistent with 5e.

Examples of applying advantage on saving throws ...

1. See the Bugbear Chief:

   ... advantage on saving throws against being charmed, frightened, paralyzed, poisoned, stunned, or put to sleep. (MM. p. 33)

   How do you make that work? Easy. Apply a spell save DC based on whomever or whatever is trying to put the bugbear chief to sleep magically. Most creatures don't get a save versus the sleep spell, but in this case you need to apply one since the chief can't apply advantage on a saving throw that isn't there; this becomes a case of specific over general (PHB p. 7). You can make it work the same way for your custom monster.

Other examples of advantage on saving throws as a creature feature ...

2. Dwarfs have advantage on saving throws versus poison; elves and half elves have advantage on saving throws versus charm. (PHB p. 20, 23)

3. Deva

   A Deva has advantage on saving throws versus spells and other magical effects. MM p. 16

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An experiential note regarding making a custom monster:

Given that you are homebrewing this, you already have room to work to make this fit in a way like the Bugbear Chief works. Based on trying to make cool/custom monsters across a variety of editions, (to include this one) I'd advise against over complicating the design. It can be tricky enough to get a custom monster "just right" already. While I'd suggest that you not tie your own hands, in the end you have to be happy with your creation.

Answer 3

There is the Warlock Eldritch Invocation "Aspect of the Moon" available to Pact of the Tome Warlocks which states:

You no longer need to sleep and can’t be forced to sleep by any means. To gain the benefits of a long rest, you can spend all 8 hours doing light activity, such as reading your Book of Shadows and keeping watch.

So, while not technically "resistance" I believe this would be what you're looking for.

Answer 4

Well, if the only thing the spells target is hit points, then it's clear what needs to be done to create a "resistance" to them:

Increase the creature's hit points.

One way might be having a feature that says something similar to:

Whenever a spell references this creature's hit points, treat it as if the hit points are double what they currently are.

It's not straight-up immunity, but still makes it harder for the spell to take effect.

Keep in mind though, that this would only be RAW because you literally wrote up the description of the racial trait yourself.

To use already-existing methods, you'd need to somehow provide a hit point increase that triggers whenever the Sleep spell (or a similar one) goes off. Something akin to a specific Contingency spell that each member of the race constantly walks around with, perhaps casting Aid at 4th-level whenever a spell invoking sleep would affect them.

Answer 5

RAW, there is no way to achieve resistance to sleep, because sleep is not a damaging effect.

Other answers have suggested:

Having the character not be able to be put to sleep (although this is not resistance, but rather immunity)

Having advantage on saves against sleep (although this is not resistance, but rather advantage, requires the invention of a sleep save, and begs the question of whether a successful save uses some of the spell's hp pool or not- see below)

and

Increasing the hp of the target for the effects of sleep

This last possibility is the closest to how the resistance mechanic works. However, the answers that suggest this have not (yet) acknowledged that hp actually affect the sleep spell in two different ways. First, the sleep spell targets individuals in ascending order of current (non-zero) hp. Second, the hp of a sleeper "use up" the spell's pool before the sleep effect passes on to the next target. Thus, advocating for a hp increase mechanism should include specifying which of these two processes are affected.

If the hp increase affects both the targeting and the pool-drain steps, the race will be less likely to be affected by a given sleep spell, but when it is affected, it will also protect those around it, even not of its race, by using up more of the hp pool available to affect the next target. This might be indicated if the OP's conception is that it "costs more" to affect this race with sleep, but it might appear unfair to the caster as it renders their spell less powerful when they have one of the resistant race as a target - in effect, the race produces a "sleep dampening" aura that benefits those around it.

If the hp increase affects only the targeting step, this would allow the race to avoid many sleep affects, but when it was affected, it would not then drain double the hp remaining out of the spell pool and thereby protect those around it. This would be indicated if the OP's conception is that the race is more difficult to affect by magic, but doesn't somehow use up the magic and thereby protect others.

If the hp increase affects only the pool drain step, this would mean that individuals of the race are as susceptible to sleep as anyone else, but when they are put to sleep they use up more of the spell (which does not seem to be the OP's intent)

While this hp doubling, when properly specified, is a workable solution, it does have the limitation that its strength is inversely correlated with the individual's need for its protection. Consider two individuals, one with this 'resistance' (affecting targeting at least) and one without. When both individuals are at full hp, the 'doubling' effect is going to be extremely powerful for the one with 'resistance' - but when both are at full hp they are unlikely to be the targets of a sleep spell to begin with. The more they are wounded, the more they will come into the range of being possible targets for the spell and thus need the protection of resistance. This formulation would certainly delay the susceptibility of the resistant individual to sleep as planned, protecting it at the first point when non-resistant individuals of equal hp around it were being affected. However, the more wounded it becomes the less protection the 'resistance' would actually give. As the extreme example, when both are down to one hp, the value of the 'resistance' will be at its minimum of just one hp, and unlikely to make a difference in whether or not the spell affects the 'resistant' race.

Contrast this with the effect of resistance to damage - there, the damage taken is reduced irrespective of the current hp of the character. The strength of the resistance does not diminish as the need for it increases.

I propose a different mechanic:

For the purposes of spells that target based on hit points, individuals of this race use their hit point maximum rather than their current hit points

This would allow one of the race to be in a crowd and most likely unaffected by a sleep spell, but still be possible to be put to sleep by a caster who could define the area of effect to include only them and/or who upcast the spell to the maximum slot possible. Thus they would be resistant, but not immune. Furthermore, by using the hit point maximum, the resistance would be at its most powerful when the individual was most wounded, in contrast to the hp doubling method.

If this ability is considered too strong as written, it could easily be modified to some variation on

For the purposes of spells that target based on hit points, individuals of this race never use less than half their hit point maximum

Note that while I have focused on the sleep spell in this answer, the OP asked about any spell that targets hp, such as color spray. My argument is consistent with any such effect.