- In my own games, I tend to follow in the footsteps of C.S. Lewis, who uses Aslan as an analogue for Christ. I've done this before, but for my Lost Colonies campaign, the fictional Christ-figure is called Isten.
- Symbols have power, especially when they convey a story. There are three holy symbols available to those who follow Isten:
Wolf Hook: This symbolizes suffering. Isten was hung upon a mountain-side by a pair of wolf hooks jammed through his shoulders.
Blood Eagle: This symbolizes both sacrifice and the single person of the God-man. When the wolf-hooks did not kill Isten, he was subjected to the blood-eagle — two slits made in the back through which the lungs are pulled out like wings. The holy symbol always features a two-headed eagle, representing both Isten's natures (God and man) in one person.
- I use bishops and priests as patrons. This is built into the way I use the Cleric class. All adventuring Clerics are deacons and are attached to a bishop. This serves to feed adventure seeds to players as well as put a religious spin on adventuring.
- I use saints...a lot. Every church and temple is dedicated to a different saint. Divine magic items are associated with/named after various saints. Religious relics behave like magic items. Characters will be visited by visions of saints and every now and then by the saints themselves. This adds a nice level of detail to the world and elevates humdrum everyday magic items into religious relics with their own unique back story.
- A major theme of the campaign is the recovery and restoration of lost religious sites. The tent-pole megadungeon is an abandoned monastery. There are lots of religious iconography, symbols, vestments, etc. that have been desecrated/left to rot. This place isn't simply a place where monsters live. It is a place which was lost.
- On the flip side, the major villains of the campaign represent and embody the seven deadly sins. Thus, these aren't just monsters the players are fighting against.
- Bonus spells for Clerics are determined randomly. This provides for a self-fulfilling prophecy. Isten gives his clerics these spells because he knows they will need them. The players want to cast them (especially utility spells that never seem to have a use) so they can get another spell. Therefore they are always looking for (and finding) a creative way to cast them — proving that they needed the spell.
- Any time my players do something religious or something out of faith, I reward them. These rewards are not mechanical — I don't roll a die or add a bonus. They are story-driven. A classic example is my players encountered a pool of acid that a chaotic tribe of humans was using to dissolve their sacrifices to a demonic image (as a rite of passage, they would cut off their own arms, which they would then replace by grafting on giant insect limbs/claws etc.). One of the clerics cast a Purify Food/Water spell (one of those bonus spells) on the acid and another non-cleric player decided to throw his holy symbol into the pool. This bit of religious action was rewarded by the pool being destroyed — it cracked and the acid drained out. Not only that, but it won over a hostile NPC who still loyally adventures with the group.
- Finally, I don't try to re-invent the wheel. Scripture uses metaphor all the time and Christ spoke in parables. In other words, these stories are applicable no matter what the context. As long as the metaphor remains the same, you can easily substitute names, items, etc. for virtually every story in the bible to make it relevant to any campaign world.