I've thought long and hard about how to make gods and their religions more important aspect of my campaigns without necessarily devoting a lot of in-game attention to them. After all, religions can add just as much to the atmosphere of a major city as its climate and architecture, and what's better than an audible gasp from the players at the first hints of Order of the Emerald Claw. But how does one go about creating this air around the table?
First, consider how to handle faith in your world (think in broad strokes):
- Intervention: The first thing to think about is how involved you want the gods to be. Are they completely removed from mortal affairs, or do they descend from the heavens at the drop of a hat? Are there any direct lines of communication to them? Is anyone even sure they exist?
- Institution: How embedded is religion in your world's societies? Is the church an ever-present influence over government, or are most faiths relegated to the shadows? Consider how each religion interacts with the other institutions in its society's power structure.
- Mythology: What is known about the gods? Are their interactions known well by the general populace, or only the learned clergy? Do they interact with each other at all, or do they each claim sole dominion over religious truth?
- Diversity: How tolerant are religions of each other? Can members of more than one religion generally be found in a single city? In a multi-faith society, always consider which religion has the most influence, and whether each faith views others as opposition or allies.
- Focus on a Few: In my opinion, D&D has a way of overdoing the whole religion thing. You don't need to make up a god for every race and class. Take the gods you're going to use, make them iconic and memorable (something a little more substantial that "the god of strength"), and get rid of the rest.
- Make it Simple: Boil your gods' dogmas down to one sentence, and play it out (with subtle variations) over and over again. If you ever change how you represent each deity, make it meaningful. Keep in mind that while you can have individuals within the faith who venture outside of these norms, your representation of the faith itself should be relatively static.
- Offer Prayer: Have NPCs pray on a consistent basis. This serves a few purposes, both reminding your players that your religions exist, and to offer the players a model of the faith in question. In keeping with the previous rule, make sure these prayers are short and to the point.
- Strong Leadership: Possibly the best way to make a faith memorable is to make the NPC guiding it memorable. Using the Order of the Emerald Claw again, one of the main reasons this cult is so compelling is its eponymous leader, Erandis d'Vol (check out the Eberron Campaign Setting if you're not familiar with this iconic cult).