How to Build a Fantasy TARDIS in D&D

Around the game table at JADE we often have conversations and debates about how to create things using magic items found in D&D. Our Submarine Project never got fully off the ground, largely because we got distracted by another idea: how could we make Doctor Who's TARDIS using only magical items from Dungeons and Dragons.

After hours of research and planning I think we have figured it out; with only a slight bending of the rules.

The first step to making a TARDIS is to make it bigger on the inside. Luckily D&D has just the Magic Item: a Bag of Holding. Since we want the TARDIS to be more of a Wardrobe of Holding, we need to do a few conversions to make this as accurate as possible. First we need the standard volume of the bag used in a Bag of Holding, then we can see how much its internal volume is increased. So, a Bag of Holding is described as a 2ft x 4ft sack which isn't very telling, but assuming the shape of the bag is roughly a cylinder with a diameter of 2 feet and a length of 4 feet that means that the unenchanted bag has a volume of 12.5 Cubic feet (Radius x Radius x Length x Pi). So, If the bag would normally have a volume of 12.5 cu ft, and a Bag of Holding as listed in the DM's guide (for any edition) has four possible volumes of 30, 70, 150 and 250 Cubic feet, then the "of Holding" enchantment increases the object's internal volume by a factor of roughly 3 and 6, and exactly 12 and 20.

Getting to our TARDIS, its external dimensions are approximately 5ft x 5ft  x 9ft. This is based off of scale measurements of our TARDIS mini, averaged against the dimensions given here on this TARDIS Construciton Forum. Those dimensions give the TARDIS a unenchanted volume of 225 Cubic ft. So using the higher end of the volume increases for a Bag of Holding (a factor of 12 and 20) that gives us a total volume of either 2700 cu feet, or 4500 cu feet. We are going to use the latter since we want as much space as possible and the guys want to go inside of this thing.

To figure out what the internal dimensions would be, we needed to to calculate the possible dimensions of a rectangular prism with a known volume. I.E. 4500 cu ft. This would have been a lot of factoring to work out given our large volume and I am not a mathematician of any sort. However, I am a system admin with access to server grade computers and C++ compilers, so I had my developer give me a hand write a few lines of code to crunch the numbers, and create a big list of all possible dimensions.

And boy were there a lot of them 
We felt the most logical set was the last one. This gave the Wardrobe an internal space 15ft x 15ft x 20ft. So this TARDIS is no where near as big as Doctor Who's, but it is enough that most parties would easily fit inside, and it would provide adequate storage for most adventures.

The next issue we had to face is that as of 3rd edition D&D and onward it is stated that there is only 10 minutes of air/person inside of a Bag of Holding. This is independent of the bag's volume and is certainly not enough time to avoid suffocation. Of course if you are playing in 1st or 2nd Ed (we are using 2nd Ed for this item) this condition does not apply as it is not stated in the rules.

However we still wanted to include a method of refreshing the atmosphere inside the TARDIS so that it could work across editions. This proved to be the most difficult hurdle to cross, however in my research (I thankfully own all four volumes of  2nd ed's Encyclopedia Magica) I discovered an item called the Cabinet of Air Refreshment. It is from Dragon Magazine 159 and details an item designed for the Spelljammer campaign setting. Originally designed to refresh the air on your Spelljammer Star Ship, a Cabinet of Air Refreshment uses the charges from another magical item placed with in it to generate 50 cu. ft. of fresh air which is enough for a crew of 12 for a week. All you do is open the cabinet, say the magic words, a charge on the item in the cabinet is consumed and the air comes rushing out. This gives you the breathable air you need as long as you have a charged magical item, and remember to activate the cabinet.

The final addition needed to make our fantasy TARDIS work is to give it some powers.  Doctor Who's TARDIS can do many different things all of which they control from a command console. To give the TARDIS different powers the easiest solution is to graft (with the use of a master craftsmen doing master level work) a Ring of Spell Storing some where inside.

Rings of Spell Storing allow any caster to load a certain number of spell slots in the ring with spells they know how to cast. Those spells may then be cast from the ring. Since the ring is grafted to the TARDIS, the two items are one and the same and so the source of the spell would be the TARDIS itself. That means you could effectively cast a Fireball spell and the box would be the source of the magic. It can also get around casting restrictions on some spells that have a limited number of people they can target. Thus, a Teleportation spell would ignore the target restrictions as anything inside the TARDIS is now part of the ring and goes with it. The only restrictions now become weight related.

We plan on using this in our Arachnophobia Campaign to allow the group to join Thomas on his Time Travel escapades, which the group is pretty excited about.

What do you think? Did we miss anyhting? Did we make the Fantasy TARDIS too powerful? Or not powerful enough? Let us know in the comments!

The 15mm scale TARDIS mini is from Rebel Minis and can be found in their Pulp Adventures section.

Written by: Andrew Gregory

How to Build a Fantasy TARDIS in D&D How to Build a Fantasy TARDIS in D&D Reviewed by JADE Gaming on 10/10/2017 02:05:00 pm Rating: 5


  1. I think this article is not considering one thing: being inside of an extraplanar space, you can't control what happens outside of it, so how can you ride the TARDIS from inside of it? When you're inside a bag of holding you can't make it move.

  2. Use a Demiplane rather than a Bag of Holding. If anybody brings a Bag of Holding inside your Chronomancer's Cabinet, you can kiss everything within 10' goodbye, but I don't know with what because your lips will also be vapourised.