Good GMs Borrow, Great GMs Steal #4: Abstract Inventories

This is the fourth of a series of posts on general mechanics you can take from one RPG system and use in another. You can find the first part here.

Abstract Inventories: What are they?

Abstract inventories are essentially ways to reduce what your character carries to something that is more manageable than planning a real backpacking trip. This is a very diverse field, but some examples include the slot-based systems of Torchbearer and Dungeon World, or the “just use what seems reasonable” system of Fate. Many people already usurp the latter for use in their D&D games, but I’d like to talk about the former methods in particular.

Traditionally, the calculation of a character’s encumbrance in an RPG relied on two major factors: weight (or mass, which on Earth or an Earth-like-planet means basically the same thing for our purposes) and volume (or size). If you look back as far as 1st edition Advanced Dungeons & Dragons you’ll find the former factor at work, while it takes only a few years more for 2nd edition AD&D to add the latter, with various bags being listed with given volumes and of course items being listed with weights in tenths of pounds, itself a practice dating back to 1e’s listing of weights in coins, which were themselves tenths of pounds.

While it is really interesting, as a sidebar, that a game primarily about thieving treasure out from under the guard of dangerous monsters would give you an item’s weight literally in gold coins so you could tell, indeed, if the item was “worth its weight in gold” or not, it is also problematic for the reasons I’ll give next.

This turned out to be a bit of a problem. Volume quickly became finicky and was for most people the first thing on the chopping block, as people hated doing Tetris in their heads. Soon afterward, weight followed, and for many it probably even went first during the time of 1st edition. The game of D&D quickly became about “just carrying what seems reasonable”, a house-rule adopted by nearly all players of D&D today and the beginnings of abstracted inventories.

However, as mentioned above, there are other ways to abstract an inventory out that are more than just based on the fiat of the game-master to say “you can/cannot carry that”, which I’d like to talk about more.

My own first encounter with abstract inventories was from The Alexandrian’s encumbrance by stone system (follow the link at the header of the article to the OD&D version to get the gist of what it’s all about, that’s a hub article), whereby you bundle items into ~10-20 lb blocks (in the case of OD&D, 15) and only ever interact with them via those blocks. Items that aren’t sufficient to warrant their own block are bundled together into a fifth of a stone, and from there you add them together into a full stone. Basically, while it ignores volume for the most part, it turns weights in tenths of pounds (meaning you’ll regularly carry around a 3 digit number, sometimes a 4 digit number if you’re rather encumbered) into weights in whole numbers that for the most part stay under 10. This is a pretty good way to do it, but I wasn’t convinced it was as good as it could be, and so I carried on looking (at the time I was in need of some encumbrance-based-gameplay for thematic reasons).

Later on I found Matt Rundle’s Anti-Hammerspace Item Tracker, which really opened my eyes to the problem of ignoring volume – you start cramming everything “in your bag”, even if it wouldn’t fit. One particularly poignant example was a story I once heard (fictitious or otherwise, you decide) of a DM who showed his player there was no way to carry 150+ arrows in his backpack by going out and renting/buying (I’m fuzzy on that detail at this point, I heard it long ago) that many arrows and dumping them on the game table. While encumbrance by fiat for volume while still using weight seems like it might be realistic enough for most purposes, in reality people make this kind of mistake all the time. Humans are generally poor at visualizing 3 dimensional space, which is why mechanical and civil engineers are put through training in that regard. The anti-hammerspace item tracker hopes to fix this by cementing items to a specific location. This means not only can you interact with them (“your backpack flies open and your rations fly into the gaping maw of the purple worm!”) better than by fiat, but you have a pretty clear limit on how much to carry. Its slot-based design is very visual. Speaking of slot-based design, that’s also what Dungeon World uses – turning weights and volumes into an arbitrary number of “slots”, which you may have X number of.

Finally, I came across Roles Rules and Rolls’ Putting Two Great Ideas Together and I was in love. It had abstracted weights and volumes into simple to use, low value, whole numbers, and it also had a sheet by which you could have definite interactions with those items. It was simple and easy to use as well as visual, and also about as realistic as one could hope for. It says a lot, of course, that a game specifically about dungeon crawling (Torchbearer) from those who gave us Burning Wheel and Mouse Guard uses a very similar system.

An addition I came up with for many of these systems is that it is very easy to use physical tokens, like poker chips or beads or whatnot, to track consumables. Having 30 poker chips in front of you makes it easy to simply discard as many as arrows you shoot – much easier and much more visceral than erasing a number on a piece of paper!

Abstract Inventories: Why should you use them?

Abstract inventories are all various ways in which you can simplify encumbrance from “pack a real backpack full of this stuff and carry it around” at one end towards “just carry what seems reasonable” at the other end. Along the way are varying levels of realism and detail, many of which I’ve discussed above, including what each of them are for. This is a more general list, which I’ll keep shorter since this article is getting quite long:

  • Reduce the complexity of tracking what you’re carrying so that you can maintain momentum when you bring it up in gameplay.
  • Find the right level of realism for the theme of the campaign you’re running. At one end are things often better suited to a more realistic simulation of travelling, while at the other end are things often better suited to improvisational games.
  • For some, simply get the concept of “you can’t carry that much” back on the table in the first place! Lots of people ignore encumbrance thoroughly in games where it might be fun, if only it wasn’t so complicated!

The House Rule Test

  1. Is the game better off with this rule than without it?
  2. Does this rule do what it sets out to do?
  3. Is this rule as simple as possible?

This is a hard one for me to do within the scope of the article because so much relies on picking the right version for the game you want to play in. Ask yourself these questions in regards to making each of the above methods fit your game if the game’s encumbrance system as written doesn’t seem to do as good a job as you would like. Make sure that it fits the theme of the game (detailed encumbrance by weight and volume in a superhero game probably isn’t going to go over very well, nor is fiat in a hexcrawl), make sure that it actually seems like it would make things better, and make sure that you’re picking the version that is as simple as possible that still does that job.

You can find further entries in this series as follows:
#2: Drawbacks
#3: Skilled Backstories
#5: All About Initiative

Posted on July 17, 2013, in Uncategorized. Bookmark the permalink. 4 Comments.

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