A god who never does anything might as well not exist from a world building standpoint. For your pantheon, decide what is considered acceptable and unacceptable behavior and whether the gods generally obey this. Each deity will have a different viewpoint, with some being very lawful, others agreeing but not overly caring, some chafing but agreeing, and others outright disdainful and either openly thwarting such rules or doing so secretly, possibly while being amused that they’re doing so. We’ll need to know our gods to make these decisions.
Do gods punish offending deities? Do guilty gods submit to the punishment (respecting the law they’ve broken) or resist, possibly by fleeing? We might decide that there’s a prison for deities and what its properties are and what, if anything, is preventing other gods, or their followers, from doing a prison break.
How do gods punish their species? Death, a nasty afterlife, misfortune, or removing talent, like one for magic? And for what offenses? Swearing with a god’s name is a good one except that so many people might be doing this that the gods would be awfully busy. Failure to undertake a promised mission makes sense for adventurers. Not defending a temple is another. Destroying one is even better. These more serious offenses are more likely to attract divine punishment. Myths about famous people who’ve suffered a given fate serve as cautionary tales that can be mentioned to spice up our narratives.
Some gods and their followers have a reputation that immediately comes to mind if they’re mentioned. A god of cruelty might force self-mutilation on its priests. For a god of love, this might be orgies. A god of wrath might be prone to outbursts of anger, making people afraid to even say his name. Does anyone demand sacrifice? Decide how people think of each of your gods (positive/negative) and why that is. Whether or not the god obeys godly rules will come into play. This is where myths can help shape their reputation, too. For some deities, this will be easier than others.
Do your gods ever visit the world and peoples they created? Why, how often, and for what? Do they have to be summoned or can they appear wherever they want? Are there restrictions on where they can go? Only other gods are likely to have created a restriction powerful enough that another god must obey. Are there time limits on how long a god can remain here? These limits should have a rationale because we assume gods are without limits.
World builders sometimes decide that the gods will not directly influence events; it’s too convenient to have them swoop in and fix things or cause issues when our characters are doing well. One way to avoid this is having the god’s behavior be that which caused the story. Past events can also have set something in motion, and this is where myths come into play, with our characters discovering the details or truth of a legend, maybe the hard way.
Gods are assumed to have invented the world and its life, whether by accident or on purpose. We don’t need to give a reason for this, but our world building can be better if we do. We can take some reasons that we have for our own creative work and attribute it to gods, such as a love of doing so. We’re curious how our children will turn out while guiding and shaping the result, so the gods can, too.
We can decide which god(s) created what life forms. This really means cherry-picking ones to make decisions about, since no one cares which god invented tomatoes, for example. On the other hand, a plant that devours species might be improved by deciding an evil god invented it, especially if it only eats certain species—namely the ones that god doesn’t like.
While a god of war is an obvious choice for the one who invented a weapon, even a god of love could do so if it’s reminiscent of Cupid’s bow. Look at your god’s trait list and imagine what items they might possess for themselves or have given to the world. Decide if there’s a limit on what can be created; maybe plants and animals are okay, but the gods must agree to invent a humanoid species. Our god of chaos might be forbidden from creating anything but do it anyway, resulting in some unpredictable monster.
Our gods can create special places, which are typically supernatural. These can be on the world, between worlds, or an alternate reality. Prisons, meeting places, means of travel, and hiding places are some possibilities. Explanations are typically better but not needed, as inhabitants often won’t know the truth; it’s unlikely they’ll even learn of these locations, but our characters will or there’s no point inventing them.
Temples, whether abandoned or not, are places where gods are likely to visit, and sometimes their religion will build these up extensively. Can the gods be reached here? Is there anything special about the place where they appear? What about the altar where sacrifices to sinister gods were made? Is a church the way to enter a portal to where that god dwells?
The afterlife is a unique place that will be covered in Cultures and Beyond (The Art of World Building, #3).