In the 1990s, British anthropologist Robin Dunbar theorized that there is a balance between the size of the human brain, and the number of relationships one person can maintain.
this limit is a direct function of relative neocortex size, and that this, in turn, limits group size… the limit imposed by neocrotical processing capacity is simply on the number of individuals with whom a stable inter-personal relationshipo can be maintained.Robin Dunbar, Journal of Human Evolution
The idea is broken down into different levels of intimacy, wherein the closer we are in a relationship, the fewer of that relationship we can adequately keep.
Humans, on average, can only maintain about 5 people at the closest level of a relationship, about 15 good friends, 50 friends, 150 meaningful contacts, 500 acquaintances, and about 1500 people we could recognize.
Something to note, if you look at the circles in the picture, the 15 includes the 5, the 50 includes the 15, and so on. Also, this isn’t the limit for your entire life, but for any point in your life. Meaning the top 15 people of your life when you were a senior in high school are not the top 15 you have when you are starting a family.
There are three types of friends in life. Friends for a reason, friends for a season, and friends for a lifetime.Eleanor Roosevelt
Now, how does this relate to Dungeons & Dragons? Well, as a Dungeon Master (DM) we are constantly coming up with Non Player Characters (NPCs) for the players to interact with. When it comes to adventure planning, knowing this information can help balance how your party interacts with different players, and how to use that to your advantage. If you want an adventure to feel small, then you know how many NPCs to stay under. If you want something to feel overwhelming, then you know how many NPCs you have to pass to reach that.
So let’s break this down, shall we?
5 Loved Ones
The most intimate circle of a relationship can hold about five people. If you think about it, there aren’t many D&D parties that are larger than six (you + your five comrades). Any time a group gets larger than six people, it’s more common that you’ll play with a less-than-full table, or you even think about splitting the party into two different games entirely. People start to lose the spotlight more often, or it gets unfairly split. While this doesn’t have much to do with NPCs, it goes to show why 3-6 seems to be the perfect party size.
15 Good Friends
Now, you can have 15 good friends, but if we remove our 5 loved ones, that leaves us with 10 people that you can have be directly involved with the party for the length of the campaign.
Who do we include with these 10 NPCs?
The Big Bad Evil Guy – This is your ultimate villain that the party is after. You might have a single villain for the entire campaign that your party is trying to become powerful enough to stop, or just the villain of this adventure. Perhaps you have Nesting Dolls of BBEGs, as your player slowly works their way up the chain of command of the villain faction.
The Mentor – Someone old and wise, who knows the world better than the players, and the party can trust will always give good information. Sometimes this person is a recurring Quest Giver, or the Party Patron if you’re in Eberron.
The Cleric’s God – Your Cleric (or Paladin) gets their power from a divine source, but it’s not just a spring of magic, but instead is a very powerful being, who not only will be called upon to help, but will also ask things of your Cleric. Knowing who this god is, what their goals are, and what types of things they’ll ask of the Cleric is important, and will not only make your Cleric feel the reality of the world, but can sometimes put them in dire straits, where the god has asked them to do something different from what the party wants.
The Warlock’s Patron – Very similar to the Cleric’s God, the Warlock’s Patron gives the Warlock powers because of a deal that was made. This could be a one-time deal, and now the Warlock can go about being who they want, or it can be a long term deal, where the Warlock has to act as enforcer of their Patron’s desires.
Between the relationships each of your PCs have, as well as the important NPCs to the campaign or adventure, I’m sure you can nail down the Top 10.
As the DM you should have deep understandings of these NPCs goals, abilities, traits, flaws, etc.
If we remove the Top 15, then we are left with 35 relationships that the party can maintain. Every time your adventure has an ally that the party likes, write them down, and be ready to bring them in later. There are a lot of options with 35 characters to keep track of. These won’t be characters that you preplan to have as recurring characters, but only when the party seems to really like a specific character, or mentions how helpful they might be in another situation.
- The Druid that helped them take down the werewolf pack.
- The Ships Captain that they defended from pirates.
- The Mayor of SmallTown that they saved, and treats the party like heroes, not mercenaries.
- The Imp that the party angered, and might come back with a vengence.
- The retired wizard who can identify magic items.
These work best when they are recurring between unrelated adventures, because it reinforces that this world continues when the party isn’t watching. When the PCs return to SmallTown, what has changed with this character that they liked. Or were one of them killed off screen, and now the party has a hook of revenge?
As the DM, you don’t need to have these character incredibly planned out, but if each one has something unique and distinct, that helps the players remember them as well. Perhaps a speaking pattern, or a persistent idea that they bring up, or anything else that makes this character stand out.
Without the Top 50, this leaves 100 NPCs that the party will meet. These are characters that are only involved for this specific adventure, and won’t become recurring characters. The barkeep, the blacksmith, the midboss, really anyone that won’t necessarily become an entire person, but just fills a role in the story.
As a DM you don’t need to worry about having these characters come back in later adventures, because the party probably won’t remember them, but at the very least try to write their name down when you make it up, because one person might say “I though his name was JimBob, not Aguthar?” and then you either show that you don’t remember, or have to come up with an on-the-fly excuse for why JimBob isn’t here, which might take your party down a completely unexpected path that might end in a really boring way.
Without the Top 150, this gives us 350 random NPCs that you might create over the course of the campaign. Many of these won’t have names, won’t have descriptions, won’t even have voices. The Town Guard you mention standing at the gates as the party walks in, the baker opening their shop first thing in the morning as you set the scene. These are set dressing, people that are the definition of one-dimensional, that should be more about creating an environment. When people say “the city itself is a character” this is what they mean. Are the children running and playing, hiding, or stealing bread? Are the sailors mean and gruff, local fishermen, or actually pirates?
As a DM, this is just your reminder that when you are setting up a place, take into account a few background NPCs that the party won’t even talk to, but helps give the place energy, or a distinct lack thereof.
1500 Recognizable People
Lastly, without the Top 500, this leaves us with 1000 more. Think about how crowds work in your adventure. Is there an angry mob, a bustling marketplace, or anything else where you don’t even mention individuals, just large faceless groups. When you describe 30 people using a word or two, these are NPCs that the PCs will see, but that aren’t even worth giving the briefest explanation of. However, at the end of the day, they do still count as NPCs, and it fills out the last of Dunbar’s Number, so it’s included in this list.