Worldbuilding, without losing track of it.

Most built worlds have one thing ours doesn’t: a magic, a technology, a strange piece of physics. What it can’t do matters more than what it can. A power with no limit solves every problem in the plot, and then there’s no plot. Brandon Sanderson makes the full case in his second law of magic.

So write the rule in one sentence and follow it outwards. Who gets rich from it? What would a careful person do to protect themselves? What stops it from running the world?

The Dry Sea’s rule is that if you hear a spell, you have to obey it. So soldiers wear earplugs, and armies give their orders by hand. Deaf soldiers are valuable, because magic can’t touch them. A city that keeps four hundred bells ringing can’t be attacked with it at all. And a spell only lasts until sunrise, which is what stops the rule from running everything.

Geography decides who can reach whom, and how fast. Three rules of thumb keep a map believable. Rivers join on their way to the sea and almost never split. The far side of a mountain range is dry. And towns grow where travellers have to stop, such as a ford, a pass or a harbour.

Then measure the world in days. A person on foot covers a little under twenty miles a day, and a large army about ten. Two cities three hundred miles apart are two weeks from each other for a messenger and a month for an invasion, and that does more for a plot than a beautiful map.

You don’t need to draw anything to begin. The Dry Sea’s places are a list, sorted west to east and measured in days on foot because, as the note on the category says, no one there agrees on a mile.

Invented worlds tend to be full of soldiers, wizards and thieves, with nobody growing the food. Before industry, eight or nine people in ten worked the land. You don’t have to show that, but it helps to know where the bread comes from, and what happens when it stops.

For prices, two numbers are enough: what a month of ordinary work pays, and what one everyday thing costs. In the Dry Sea a soldier earns three bits a month and a goat costs four. The soldiers know a goat is worth more than they are, and there’s a marching song about it.

The most common weakness in invented cultures is one trait per people: the warrior people, the merchant people, the wise people in the forest. Real societies argue with themselves, so give each one something its members disagree about.

Customs come more easily once you know the pressure behind them. People with little water have rules about water. People living under a magic that works by sound have rules about noise.

For whole powers, three facts go a long way: where they’re from, what they speak and whose side they’re on. In the Dry Sea, the Ninth Regiment stands with “whoever eventually pays them”.

Readers hear a culture in its names before you’ve described it. You don’t need to invent a language for that, only a few rules for each one: which sounds it favours, how names end, and how a full name is built.

The Dry Sea’s naming note is seven lines long. Highland names end in -ak, -uy, -ay or -oy. Delta names are a given name, then “oss”, then the mother’s house. People from the sea take their ship as a second name. Soldiers go by nicknames in plain words, and if one needs explaining twice, it’s the wrong nickname.

Then think of the reader, who meets these names by eye. Start your main characters’ names with different letters, keep them sayable, and go easy on apostrophes.

A thousand years of kings is easy to write and hard to use. The history worth having is whatever someone in the story is still angry about, still paying for or still lying about.

Let people disagree about it, and let it get vaguer with age. The Dry Sea’s oldest event is dated “6,000 or 11,000 years ago, depending who’s shouting”.

Settle the calendar early, though, because weeks and months turn up in dialogue from chapter one. A line in the Dry Sea’s revision notes reads, “Do they have Tuesdays?”