Gods are real in the fantasy world. We know that. Clerics specialize in channeling their power. Unlike on Earth, gods in our fantasy works can be proven almost on demand, as they affect the world in immediate and substantial ways. But usually what you get in most worlds are hegemonic panteons over nations and empires, with a handful of gods, maybe a dozen. And they’re distant and part of the campaign background. But the nations in this world don’t need to convince anyone of the reality of their god, nor any others, as the gods make themselves evident. Any holy war is a conflict between actual gods spreading to their followers, not a war on who’s right about the true faith: both worship real gods, just my real god wants your real god out of the game
I guess my point is that the gods you learn about in a campaign setting or we sketch for our worldbuilding probably aren’t our Player Character’s gods. They’re the gods of kings and princes, uninterested in the matters of smaller gods. But there are smaller gods, hundreds of them. Immortal, immaterial, local, and limitedly powerful. Why doing away with them? They’re real, and if you’re a god steering a nation or guiding your paladins to battle you do need someone to keep the ponds fresh and the fields fertile. As long as they’re aligned with you, they can gather the faith of the commoners.
The gods of low level characters are everyday gods. There are hundreds of them, each day of the year holding the festivities of at least five, and that only considering the ones registered in your kingdom’s archives. Local and with a small field of power, there are as many gods as there are creeks, villages and hills. Each rural population has at least a few local deities of various spheres of influence: this village has a small god of passionate love and stinging insects, but this other village has a frog spirit that is said to be better at long term love.
They’re all, of course, immortal and should be feared by mortals, although their powers could be limited. They could or could not be able to show themselves in humanoid form or speak through a deer or the wind or dream message. They might be able to change the river’s color or attract hunt or make teenagers fall in love and they can’t be damaged by mortals, but they probably can’t do much to them either other than inconvenience or an occasional curse. Still they are real and they hold real and convenient power. Most village clerics worship mainly their local deities as a mixed general “Law” faith. Their powers are similar to 1st and 2nd level spells, except they can exert them with no or few limits, of course. They’re gods, after all.
These gods can and should appear in your games, as frequently as orcs or kobolds. They can be part of a puzzle, a nuisance, a comic relief, part of a local plot or a dungeon. A door only opens if you offer the god some honey. And this oak’s spirit will tell you how to enter the tomb. A local god of cooking makes this tavern’s food delicious but it loses all flavor when it gets out of the village. Here we have benevolent goblins because a Lawful goblin god of kindness lives by the crossroad. And by our fields the plains are confusing, 5 in 6 of becoming lost, because of our trickster god of wind and grass. Use them to define different world rules and expectations for different places, for interesting encounters or as a way for almost anything mysterious happening. They can teach spells, provide boons or give minor magic items. Add “minor god” to your wilderness encounter tables.
When gods are more talented, powerful, interesting or otherwise successful, they gain some popularity beyond their immediate surroundings. They can be worshipped throughout larger regions, usually by the “best men”: city dwellers, minor nobles, merchants, artisans, officials and readed people. They encompass more useful or wider spheres of influence and have more active agendas, so they don’t have much time for the smallest issues of the peasants. The god of textile commerce. The lady of bridges. A spirit of pestilence protecting the faithful from bad sewer work, and a deity of convenient and punctual marriage. They are more powerful, 3rd or 4th level spell equivalent, and their influence and agendas can shape the culture and aspect of your region and its politics in very sharp ways.
Yes there are gods of magic. They don’t take clerics, but wizards instead as servants.
Use them in your urban plots and your first intrigues. They can be behind a main antagonist or become quest givers or benefactors. They’re the kind of god that the castellan and their men are most close to, so picture how The Keep in the Borderlands would change if the castellan had a favor and service relation with a god of discipline and accountability or a god of adventure and discovery. They can convey the major themes of your region being an active part of the adventures.
These are the big ones, the small pantheon with the official kingdom holydays. Big hitters doing their stuff with only a handful of another pantheons competing with them in the world. Here we find the father, mother, queens and king of gods figure, with their direct families plus a few other big powerful ones. They encompass spheres of influence such as war, love or death, and they have followers all along the kingdom, often through many kingdoms. Of course they only interact directly with the most powerful and influential mortals, and a cleric in contact with one of them hit the jackpot and can be considered a true Patriarch.
These are the background gods we’re used to, outlining the general themes of the campaign world and the bigger potential plots once our PCs mettle with monarchs, emperors and other high power characters. They are also good Big Boss antagonists if you get your campaign to survive that long. They spark the holy wars and protect or threaten the plane.