Is there light inside a Bag of Holding?

Question

My question is fairly simple: is there light inside a bag of holding? I'm asking this because I'm trying to do a passive run and I plan on storing unconscious enemies in the bag.

I know that living creatures suffocate after 10 minutes depending on how many there are, but my plan is this: if I can grow algae, (a few kilograms per person including water) then the algae should be able to filter out CO₂ and other toxins while adding oxygen to the air. This whole plan hinges on the fact that there is light (preferably sunlight) so that the algae can perform photosynthesis and stay alive.

I don't know that much but from what I've heard the bag links to a separate dimension and I wasn't sure if this dimension has light or not. I tried really hard to find out the answer before asking but I couldn't find anyone else mentioning this very specific question.

Answer 1

Light or not in the bag is not explicitly stated in any rules. With the bag otherwise behaving a lot like a normal bag, I would assume not. You could just put something glowing brightly into the bag though, if you have something appropriate (IMO would need to be bright as daylight).

It is risky to apply too much scientific analysis to items in a fantasy game. Many things in D&D do not make sense if you think about them too hard. It is best to remember that the air being breathed is fantasy air, and any plants you have are fantasy plants. Although fantasy plants no doubt grow in the sunshine, and creatures can suffocate without fresh air, there is no need to invoke scientific understanding of these things such as photosynthesis and oxygen.

One thing to do is present your plan to the DM and hope that they will go along with it. Sometimes a few nods to science and clever plans are all good for a game. Just don't get too bogged down in it. Also accept that between the whole group, your ideas probably won't be too accurate, or you will miss an important detail. For instance, do you know how much algae would sustain a person (assuming bright sunlight), and do you care to research it? (I think around 6 litres of algae-rich water is right from a quick search). How would your character know this?

Better still, find a game item that does what you want mechanically more directly.

Answer 2

Jump in and have a look

The rules don't say so this is up to your DM. The easiest way to find out is climb in the bag and have a trusted friend let you out before you suffocate.

By the way, your plan won't fly in my campaign because I would require your character to explain just what type of magic, oxygen, carbon dioxide and photosynthesis are and how they know about them. People in my bags of holding don't die due to lack of oxygen: they die because it says they do.

Answer 3

It's dark in there

There is no light inside an empty Bag of Holding. The inside of a Bag of Holding is a closed space, sealed off from both the Prime Material Plane and the Astral Place. It's effectively an air-tight chamber in extra-dimensional space.

We know this because while the Astral Plane is filled with "something sweeter and perhaps more solid than air" that sustains life (Astral Plane, DMG, p. 46), inside a Bag of Holding:

Breathing creatures inside the bag can survive up to a number of minutes...

DM Guide, p. 154

(The fact that you can easily suffocate inside one of these things is a big tip-off that it wasn't meant for you to get inside, and accommodations like lighting shouldn't be expected.)

As the medium of the Astral Plane that sustains breathing does not extend into a Bag of Holding, we can assume the glow that allows creatures in the Astral Place to perceive an "endless silver sea" (DMG, p. 46) is also absent from the bag's interior.

Additional Magical Effects should not be assumed

Magic items resemble their mundane counterparts except as noted in the rules. (That is to say, a magic sword can't brush your teeth, no matter how good a magic sword it is.) Light is not mentioned as a magical effect in the bag of holding's description. It follows that the interior space of a bag of holding would resemble the interior of any other sealed bag.

Special Magic Items

This answer seeks to give guidance based on the best info we have in the rules. But magic items in fifth edition are meant to be unique and special. So, if a DM wants a bag of holding to be lit in the interior, or to have whatever effects, then certainly, rule 0 applies in spades to this.

Answer 4

No. A bag-oh-holding is connected to an extra-dimensional space practically created specifically for this bag-of-holding. You could put a light source into it though, such as a rock with the Light spell cast on it.

Answer 5

I don't believe there's a RAW answer to this, but I would tend to assume there is not automatically light inside the bag.

However, you could certainly store something in the bag that emits light, such as a small stone that has had the Continual Flame spell cast upon it (or, if Continual Flame is deemed insufficient for sustaining the algae, you could instead use Daylight, if you had a way to cast it 24 times per day).