I’ve been re-reading the comic book series Elfquest lately, the setting of which is usually referred to as the World of Two Moons — for the very simple and obvious reason that there are two moons in the sky.
This is surprisingly rare in fantasy.
Science fiction, sure. Having multiple moons in the sky, or multiple suns, or planetary rings, is a quick and easy way to signal “alien world” to the reader. But in fantasy it’s almost always just one sun and one moon, lighting a world that is either a round ball or unspecified in shape. I can name a few exceptions, of course. Terry Pratchett’s Discworld is famously named for the fact that it really is a flat disc sitting atop the backs of four elephants which themselves stand on the back of the great turtle A’Tuin, who swims through the void of space. Voyage of the Dawn Treader, the third* book of the Chronicles of Narnia, features the protagonists sailing to the eastern edge of what appears to be a flat world. And in Elizabeth Bear’s Eternal Sky trilogy, the contents of the heavens depend on whose territory you’re in; cross a border (or get conquered), and the sky can change completely. I’m sure there are others — feel free to suggest some in the comments! But by and large, this isn’t an aspect of the world that most fantasy writers bother to fiddle with.
I can think of two reasons, coming at the situation from opposite directions. (Well, three — the third being that it never even occurs to the author to play around with this aspect of their setting.) First, some writers feel they would have to address the scientific underpinnings and consequences of making such a change. Taking two moons as an example: what does that do to the tides? Can you have rings around an Earth-like planet, or does that only happen with a gas giant? Etc. When you’re writing planetary science fiction, there’s more likely to be a general expectation that you should get those details right, and not everyone will want to go to that extra level of work. And since we all have things we get hung up on, a fantasy writer may likewise feel that they should pay attention to the science . . . even though nothing says your invented world has to behave the same way. If the bands across the sky are the shattered remains of the gods’ enemies, the land they arch over can take any form you like. If tides are caused by the yearning of the sea goddess to return to the land that rejected her, then what does it matter how many moons are in the sky? Heck, your story may not even take place in a coastal location where the behavior of the tides will matter.
This brings us to our second possible reason, which is that the writer may not see the point of messing around with basic world-shape elements. From this perspective, if your whole novel takes place in a single city, then whether the world is a round ball or a flat disc or something else is irrelevant to the story. Having multiple moons would at most be a throwaway detail. Planetary rings, or something that looks like them, are just one more thing you have to describe to the reader, which may distract them from the plot and setting elements that have real impact on the story.
Your mileage may vary, but I’m a fan of throwaway details, those little side notes that give the setting flavor without being load-bearing. Especially because everything in the setting is interconnected: even if the shape of the place isn’t directly tied into your plot, it will still affect the way the characters live and speak. In Elfquest the main characters refer to the two moons as the Mother Moon and the Child Moon; you’d get a different vibe if they were instead called the Hunter Moon and the Prey Moon, or the King Moon and Peasant Moon. So even a passing line about “the moons were thin crescents, and the Hunter Moon had almost caught the Prey Moon” adds color to the setting — a very different color than you’d get if instead “the moons were thin crescents, and the Mother Moon was cradling the Child Moon in her arms.” Speech will reflect these basic details: people may not use phrases like “around the world” if their world isn’t a round ball. If their creation story follows the “emergence” pattern like the ones common in the American Southwest, with humans climbing up through a series of different worlds before settling into this one, that could be reflected in everything from architecture (the small hole in the floor of an underground kiva represents the portal they came through) to their annual festivals. If you’re writing very epic fantasy, your characters might go back down through that hole to the world below — but even if they don’t, those beliefs will still shape everything around them.
I’d love to see more fantasy authors play around with these fundamental structures. Give me multiple suns, multiple moons, planetary rings or something that looks a lot like them. Give me flat worlds. Give me worlds that are round balls — with everyone living on the inside of that ball, and the sun stationary in the center. Give me worlds that are long interlaced bands, and you can leap across the gap between one part of the band and another if you know what you’re doing. Give me suns that are fiery chariots being driven across the sky, and then dangerous underworlds they have to traverse before they can bring the next dawn. Give me moons that literally are eaten by the darkness and then re-emerge, having temporarily defeated their foe. Because if you’re writing fantasy, there’s no reason that can’t be true. No reason you can’t take the ideas of mythology and treat them as the actual, functional reality of the setting, with all the consequences that implies. Richard Garfinkle did this brilliantly in Celestial Matters, where Ptolemaic astronomy is 100% correct; I’d love to see more authors do the same.
*Publication order. I will fight you.