Okay....to make an extremely long story short. A PC put an imp inside his bag of holding. Running out of oxygen I made the imp transform into a spider to survive a much longer time than 10 minutes. (Looking online this imp/spider can now survive weeks with little oxygen)

At some point my PC also added a head of an immortal being inside the bag of holding. (The imp is assumed to be long dead to due to the lack of knowledge of its transformation ability)

So some bullet fire questions to help me as a DM to know if it's allowed (and have some back up that this is not "too bs" for the players)

1. He will take that head out at some point
2. That head will have a spider in its mouth/ear/neck-hole whatever
3. The spider will crawl out of it's hiding spot and transform back into an imp.
4. The Imp will take the head and go invisible while holding the head and escape.

The stuff I listed, do any of these break the rules that's currently in place for the game? imp's invisibility, transformation, bag of holding functions and etc.

## The imp can't survive for long even transformed

The imp inside the bag of holding has 10 minutes of air as usual, according to the bag of holding description:

Breathing creatures inside the bag can survive up to a number of minutes equal to 10 divided by the number of creatures (minimum 1 minute), after which time they begin to suffocate.

Note how it doesn't matter how much or how little oxygen a creature requires. The rules do not make such a distinction or go into this much detail. 10 minutes are assumed regardless of whether the creature is a tiny spider or a large bear.

Transforming into a spider also does not help the imp in this situation. The imp's transformation does not really change much:

Its statistics are the same in each form, except for the speed changes noted.

This means that it always keeps its Constitution of 13 which does not allow it to go without oxygen for weeks unless you are making a specific exception in this case.

## Even if it can survive, you probably want to reverse the action order

Note that both Shapechanger and the Imp's invisibility require an action. It is probably advantageous for the Imp to turn invisible first, possibly even while still being inside the bag of holding, before transforming back into its normal shape and trying to get away with the head.

• You ninja'd me! Nice answer and good to clarify the suffocation rules for OP +1. Commented Dec 2, 2019 at 16:59
• so when it shape changes, it's casting the polymorph spell? I thought it just followed the spells effects ignoring the semiotics, material, and concentration. Kinda like how the Duergar enemies are able to use "Enlarge" spell without holding concentration or the stuff needed for that spell too. Commented Dec 2, 2019 at 17:08
• @Rugiewit That quote I have placed is part of the description for the Imp's Shapechanger ability. It is not a spell at all, it does what it says in the description and that's it. It's just an ability. In that context, the word "polymorph" is being used as a verb, it is not referring to the spell by the same name (it would have say "it casts the polymorph spell" or a similar thing for it be the actual spell.)
– Sdjz
Commented Dec 2, 2019 at 17:47
• Do imps breathe? I thought there would be something in the stat block to distinguish a "breathing creature" from a "non-breathing creature", but I don't see anything. Commented Dec 3, 2019 at 3:04
• Or do the rules-as-written just assume that all creatures breathe, and therefore I can suffocate a skeleton or a suit of animated armor? Commented Dec 3, 2019 at 3:23

Assuming it hasn't asphyxiated, the imp-spider will have to use its action to Shapechange back into its normal form.

Shapechange: The imp can use its action to Polymorph into a beast form [...] or back into its true form.

The next turn, it will have to use the invisibility action.

Two actions, two turns. Your party will have a chance to react to the imp's shenanigans.

• Imps are pretty intelligent and one could plausibly rule that it would maintain invisibility to remain undetected in the event that the bag is opened or turned out thus falling out with the rest of the contents. And you seem to imply that the imp would have to change shape first, nothing prevents the Imp from casting invisibility while in beastform does it? Commented Dec 2, 2019 at 17:51
• @Slagmoth Potentially, yes. The imp would have to reuse invisibility every time it wakes up since it requires spell-like concentration to maintain. Commented Dec 2, 2019 at 17:57

While sdjz's answer nicely handles the "it'll suffocate" part, I have an alternate scenario.

## Since the form of the imp doesn't matter, why be a spider at all?

Given that, regardless of shape/form the imp is using, it can only exist a certain amount of time, then why shape change at all?

Keep the imp as an imp, but stay invisible in the bag. When the bag is opened to put the head in, the imp grabs the head and re-invisibles itself along with the head. When the party opens the bag to retrieve the head, both head and imp are invisible and can fly away.

If the imp waits until the party removes the head, the imp would need to a Strength contest to wrestle the head away from whomever pulled it out. And with a -2 to Strength, it wouldn't be much of a contest. So best hide the head when no one is around.

As a side note, there is no RAW one way or the other that items placed in a Bag of Holding can even interact. So if you throw in dirt and later throw in water, will you get back mud? Or can you retrieve each separately?

The closest idea I can find is with the Handy Haversack:

Placing an object in the haversack follows the normal rules for interacting with objects. Retrieving an item from the haversack requires you to use an action. When you reach into the haversack for a specific item, the item is always magically on top.

Using the phrase "on top" would imply that there is something below it. Otherwise it would be phrased to say that it is the only thing accessible. So things in the Haversack do touch; at least at some point. But that is not a for-sure, and for a different, but similar, item.

• I'm not sure that the imp can interact with outside the bag while it's in the bag (assuming it's been a short enough period to still be alive.) Can you support that a creature in the bag can interact with things outside the bag when it's opened? Commented Dec 2, 2019 at 18:09
• @NautArch, there is nothing RAW either way about creatures interacting with other objects within the bag. I'm just using the same logic as the original poster. In step 2, "That head will have a spider in its mouth/ear/neck-hole whatever" therefore it is assumed that the spider would have access to the head to crawl inside. Personally I don't know if I agree with that ruling, but haven't had a reason to make a decision. Commented Dec 2, 2019 at 18:23
• Up to you, but usually better to clear up any misconceptions OP may have (or explain them), then go with their assumptions unless they've specifically stated that they're using some sort of houserule we don't know about. Commented Dec 2, 2019 at 18:27
• @NautArch, normally I agree. But as I stated, there is no RAW information regarding the inner workings of a Bag of Holding, I cannot clear up that assumption. The closest there is is with the Handy Haversack which I can add as a side note. Commented Dec 2, 2019 at 19:16