In creating a fictional polytheism, it’s useful to have a sense of what kinds of gods are possible.
The honest answer to this is “anything you like.” There’s nothing inherently wrong in a fictional setting that is clearly unlike the real world; if you want to posit a theology where the three divine forces are the deities of acute angles, obtuse angles, and the right angle who rules over them all, you totally can! But in most cases, authors aim for something more like verisimilitude. Which means understanding what kinds of divine forces we tend to worship, and why.
Celestial gods come first because they dominate many pantheons. We’re often impressed by the sky: it’s above us (which frequently connotes power and authority), and no matter how high you climb, you can never touch it. The sun is a source of life, while the moon pulls this amazing trick of withering and then growing again, and the stars are the original Rorschach ink-blots, inviting us to imagine pictures in their arrangements. We use these celestial phenomena to tell time on levels ranging from individual days to seasons and years, planting and harvesting and ordering our lives by the dance of the sky. It’s also the source of rain and the awe-inspiring powers of lightning and thunder. Small wonder we pay it such reverence!
Of course, the earth is important, too. Any society that relies on agriculture will be praying for the fertility of the earth; hunter-gatherers care about that, too, along with an abundance of game. Below that — spatially, not necessarily in importance — you find the chthonic gods, those associated with the underworld. In many cases that means death, but the earth also contains a great wealth of precious metals and jewels, and it isn’t hard to rub out the line between what’s under the earth and what grows on top of it.
Looking not at what the land produces, but what it represents, you also get the category of sovereignty gods — or in many cases, sovereignty goddesses. These show up especially in Irish mythology, where the king’s blessing by and/or sexual union with the goddess who represents the land is key to the legitimacy of his rule. Ireland being an island, it’s easy to put boundaries on where that goddess’ power applies, but there’s interesting potential in playing with this on a larger landmass: what happens to such a deity when the borders of a state move?
A sovereignty figure is one subset of a broader category called tutelary deities, i.e. guardians of some particular target, whether that’s a place or a person or even a specific activity — that last shows up in the role of Catholic saints as patrons of different occupations. In Latin, gods of places were called genius loci, but the idea isn’t restricted to the Greco-Roman sphere; Shinto often has kami of specific mountains and such, Chinese folk religion has the City God and the Lord of the Soil and Ground, and Hinduism likewise has gramadevata. These are only worshipped in their own localities — unless the people from that locality wind up running the whole region, which at least in some cases seems to be how pantheons get constructed: the ruling group’s tutelary deity winds up being the chief deity for everybody else.
As that shift implies, sometimes tutelary deities are linked not to places, but to particular clans or lineages. Or rather, they can be both at once, courtesy of the strong ties a family may have to a particular place — and this blurs pretty easily into the category of deified ancestors. Along with this, people may have their own individualized gods, which is the original meaning of “genius,” and which gets inverted with Islamic notion of the Qarin or Qarinah, a companion jinn that tries to turn a person toward evil. You also have a whole swath of minor household gods: either the little deities of important objects in the house like the hearth, or more generalized entities like the Roman Lares and Penates or the Russian Domovoy. Some theories about domestic faeries like brownies suggest that they’re the surviving remnants of ancient pagan household gods.
Looking in the other direction — away from the personal and daily to the ancient and remote — primordial gods are deities linked with the very earliest stages of creation. In many cases these are not worshipped any longer; they may even be enemies overthrown by later gods (which may echo the prehistoric conflicts between different groups of humans). And Greek mythology in particular was fond of personifications, “deities” of abstract ideas who were not so much the focus of actual worship as philosophical constructs used to discuss the world.
This question of worship is an important one. Not everybody is going to worship every god, and not every god will be worshipped in the same way. The study of Greek religion makes a distinction between Olympian and chthonic gods in part because the practices used to worship them were different: chthonic deities often received their offerings in pits or underground chambers, and the sacrifices were given up entirely rather than shared as a meal among worshippers. A household god may be placed in a niche and given a bit of incense or a sprinkling of water each morning; it’s not going to get the elaborate yearly festivals of the city god.
But the other thing to bear in mind here is that these categories are far from rigid. Next week we’re going to look at the ways polytheism becomes messy; for now, bear in mind that gods may have both celestial and chthonic aspects (Demeter received both Olympian and underworld-style worship, depending on the place and the time), that the tutelary deity of a locality may also be the patron of a particular occupation or associated with a celestial phenomenon, and that some “deities” may exist largely for the purpose of braiding more relevant powers together into a family tree. Nor is this anything like a complete list, since I made no specific mention of things like gods of the sea or tricksters (those are going to get their own essay someday). Hopefully it gives you food for thought, though!