Can a vampire rest in a coffin in a bag of holding?

Question

I'm thinking about my vampire organization - if they have placed a coffin inside a bag of holding (sized to fit) and then climb inside, do they have a portable place to rest?

Answer 1

What the book says: this will work

As long as the vampire moves some grave dirt or their coffin they can rest. The Monster Manual says:

Chained to the Grave. Every vampire remains bound to its coffin, crypt, or grave site, where it must rest by day... A vampire can move its place of burial by transporting its coffin or a significant amount of grave dirt to another location. Some vampires set up multiple resting places this way.

A vampire is bound to their grave site whether that be a coffin or just the dirt they were buried in. These materials must be moved to the bag of holding to create a new resting place within.

It's your world

Vampires have different rules in a number of different fictional worlds. The rules a vampire abides by in your world can have whatever rules you set to them.

Answer 2

You will need to decide what 'by day' means inside the bag

Other answers have confirmed that the physical dimensions of the bag are sufficient and that the vampire does not need air. The bag also has a weight limit, but there is only so far we can take that analysis since we do not know how much a vampire weighs.

However, there is a final variable that has not yet been addressed. A vampire's chained to the grave feature makes its rest interact with cycles of day and night in some specific way.

Chained to the Grave. Every vampire remains bound to its coffin, crypt, or grave site, where it must rest by day.

The use of 'must' here is odd. The most natural English reading would be that a vampire or vampire spawn is, during the day, required to return to its 'grave site'. And yet we know that this is not true; vampires in official products can be active during the day, so long as they remain careful to not be exposed to direct sunlight.

The vampires and vampire spawn in Curse of Strahd, for example (bearing in mind that the sunlight of Barovia is so weak that it does not harm them), can be found resting in coffins during the day but may also be found explictly active during the day.

Thus, it seems like what 'must' means in this context is that 'if a vampire or vampire spawn is going to receive the benefits of a rest, then it must be both during the day and while they are in their grave site'. They do eventually need to sleep, and although they are not required to take a rest any more than than any other creature (unless they have been defeated), in order to rest they must fulfil certain conditions.'

So, when vampires choose to (or are forced to) rest, they must do so by day. Which brings us back to the bag of holding, because the inside of the bag is an extradimensional space. As such, it is not under the influence of the day and night cycles of the separate world in which the exterior of the bag exists. The inside of the bag shares a common time with the outside, but it is a different place with no sun, day, night, or dawn.

So, if a vampire can only rest during the day, does it receive the benefits of a rest when it is in another dimension that lacks day and night? Is the presence of its grave site enough? Fortunately it is your world, so you get to make that decision.

Answer 3

Yes, vampires don’t breathe.

Vampires have the Undead Nature trait, which is unfortunately below, not in, their statblock in the Monster Manual:

Undead Nature. Neither a vampire nor a vampire spawn requires air.

Ergo, the environment inside a bag of holding poses no challenges for the vampire.

Answer 4

It depends on what you mean by "sized to fit"

The dimensions of a bag of holding are given as follows:

This bag has an interior space considerably larger than its outside dimensions, roughly 2 feet in diameter at the mouth and 4 feet deep. The bag can hold up to 500 pounds, not exceeding a volume of 64 cubic feet. The bag weighs 15 pounds, regardless of its Contents. Retrieving an item from the bag requires an Action.

So you are looking at cylinder with the opening being a 2 feet across circle and only going 4 feet down. According to this site , a typical casket has an exterior width of 29" and exterior length of 84", which is 5" too wide to fit through the opening and a full 3 feet too deep! These caskets have an interior dimensions of 24" wide by 79" long (6'7") and can fit someone up to 6'10" due to some compression/folding/etc.

There aren't explicit sizes listed for children's, only "anything smaller", but we have an exterior minus interior width of 5" and exterior minus interior length of 5", so we can assume the thickness of the wood/handles/etc add 2.5" in all directions. You could in theory skimp on this by having an ultra thin coffin, maybe made out of better materials. Say that takes you down to 1" in each direction, that saves you 4" of length and width. You'd have to lose 1" of width space on the inside, doable without much problem. But to get down to 48" total length with 1" top and bottom means 46" of interior length, compared to the standard 79". That's a reduction of almost 40%. Assuming that reduction scales directly to the height of a person it can handle, that would mean the 4 ft long external coffin (with tiny thin 1" walls) could only handle a vampire 49.8" tall, or 4 feet, 1.8". So...a small or child vampire?

Let's say you go the grave dirt dirt route instead. First, it's up to DM call just how much grave dirt you'll need in there. Then there's the fitting of the vampire. Squeezing into the 2 feet wide entrance, then crouching inside/folding themselves up to get under 4 feet in height while remaining no wider than 2 feet in any dimension is beyond the scope of my research right now, but assuming the vampire is relatively athletic and thin and perhaps has some contortionist training, it would probably be doable.

The other answers address the surviving the environment (Vampires don't need air, and just what does a vampire need to survive: Coffin or "grave dirt")

It also depends on just what the dimensions of the bag of holding are

as @MJ713 pointed out, the 2 foot radius 4 feet deep cylinder does not have the required 64 square feet of volume. 4 feet of depth would give 16 square feet of width, which given D&D's penchant for cubes and spheres, is most likely a 4 ft cube. If that is the case the radius is given just for the gateway of the bag. Then the actual longest dimension inside would be from two extreme corners, which gets you to 4 times the square root of 3 ft, or just over 83". So, if one is able to carefully lower the coffin into that notional cube, assuming that's what the DM rules the inside is past the narrow opening and into the longest dimension, a standard coffin would just about fit. Now, the standard coffin is 23" high, and wedged into the corner you would have problems opening it. However, if you custom built the lid you might be able to get one that you could squeeze inside and still get in and out of, even more of a DM call...or a job for AutoCAD. As a mathematician and not an engineer, I'll leave that to someone else.