I thought I’d share here a short list of four maxims that I use for good fantasy world building to flesh it out in a believable way that makes a setting come to life as a distinct world.
1. Internal Consistency, not Realism, is the benchmark of a believable fantasy world.
You don’t need to make your world realistic to make it believable. What is key is that the elements in your world are internally consistent. Whenever you add an element to your campaign, be at a race, city, country or person, always ask yourself the following questions:
Where did it come from?
How does it affect the elements around it?
How do the elements around it affect it?
Also take time once in a while to consider how the various layers of your world interacts. If ogres are accepted members of society, this is probably gonna affect fields of hard labour and what makes a better cityguard than a band of ogres? In my world for example, there are no half-elves or half-orcs. This affects how closely elves and humans interact and segregates them more as races.
You don’t neccesarily need to write these things down, but you need to have an idea of this as you go along. In fact, as you add more and more elements to your world, it becomes a very helpful tool for you as it becomes much easier to place new elements in your world in suitable places where you know it makes sense for them to be there.
The real world is obviously a great source of inspiration for this as it is a model example of a world that is internally consistent, but you need to consider how things such as gods, magic etc. affect natural and sociological laws. In fact, in a world that really is created by gods, it might even make sense to disregard natural sciences as valid. A quick real world example are the fundamentalist Christian sections of American society that have a hard time coming to terms with theories like evolution. Why? Because it doesn’t mesh with how God is said to have created the world.
2. Focus on what can be known.
Unless you are in it for timewasting, don’t bother wasting time on details no one is ever going to know about. It doesn’t matter where your main continent lies in relation to the southpole unless global exploration features in your world (only world I have ever seen such a detail relevant for is Mystara).
Contrary to how it might initially appear, this isn’t an encouragement to be light in detail. But make sure that you focus your level of detail on aspects of the world that players (or readers, if you write stories set in the world) come into contact with. If you combine this with paying attention to internal consistency and find ways of illuminating of these details connect with other elements in your world this helps players connect with your world and makes it come alive, as they interact with living systems instead of random elements.
Focusing on what can be known is focusing on demonstrating your world to your players, so as to not merely be a geographical and cultural backdrop for adventure, but a setting that permeates their actions and lives at every step in a meaningul and coherent way. This doesn’t require the level of detail of Tolkien’s Middle Earth. In fact, one easy trick to use is:
3. As made above, so seen below.
This is really just an extention of the two maxims above, but one worth mentioning on its own. When you devote time to thinking about the more general elements of your world, cosmology, how magic works, how nature works etc., don’t just take time to conceive how this connects with the world on a lesser scale, but make sure to create elements that actively demonstrate these things.
If magic works because of the power of words, make this an integral part of the culture. Nicknames are common because one’s true name is not lightly revealed and knowledge literally becomes power.
If the weather and terrain is governed by spirits (or are spirits), how does this affect settlement and agriculture? Perhaps an empire has grown rich because it subdued its spirits to make the land bountiful. Maybe dwarves communicate with the mountains to provide them riches through secret runes and rituals known only to them.
This makes it easy to create unique elements that permeate every facet of your world and distinguish it from other worlds in the experience of your players.
4. Be willing to disregard consistency in favour of a good idea.
This might seem like an odd maxim, but the fact is that it is often far easier to throw a good idea into your world and then adjust its internal consistency to make it work than it is to come up with a good idea that will fit into the consistency you’ve conceived of your world so far. This is something to pay attention to mostly in the preliminary proccess of creation. Once you open the world up to others, this obviously only works with elements known only to you.