"Face it, the cleric is usually the guy who shows up last to the gaming table, a big, stupid smile on his face, saying 'Hey, guys, I want to play. What's the party need?' To which, everyone replies, 'We need healing. You're the priest. Shut up and sit down.'"
-Foreward to The Cleric Quintet by R.A. Salvatore
In D&D, the cleric is arguably one of the most important character classes to include within a group of would-be adventurers, while also presenting a number of problems for a DM. Possessed with the ability to channel divine energy into healing and curative spells (as well as other fun stuff like fire and brimstone), a cleric is a must-have for any group planning to go off in search of bitey, stabby and/or other types of killy things. They are often seen as heal-bots by players... so, what about by NPCs?
Making the rules for cleric powers mesh with a dangerous and exciting fantasy world becomes problematic when applied to the world as a whole. The rules for cleric PCs assume that the character has a direct conduit to his or her god with the ability to use that divine influence to answer prayers in the form of spells. As long as the cleric isn't doing something heretical or otherwise naughty, these prayers are expected to be answered, no questions asked.
PCs also seem to expect clerics to be readily available in local cities, towns and villages to disperse healing potions and handle any maladies they are not equipped to resolve themselves. (i.e. they expect town heal-bots to be higher level than they are.)
The structure of these rules makes a lot of sense from a gameplay standpoint. Adventuring groups need a way to recharge and stay alive during dangerous delves and overland excursions. Making the gods' wills more capricious or the nature of their existence more nebulous would likey prove frustrating (maybe they only answer 1 in 10 prayers) resulting in frustrated players and a loss of fun.
From a worldbuilding standpoint, however, such rules raise the question, "What do these clerics do when they aren't healing heroes. Do they use their healing powers on the regular townsfolk?"
How would such access to divine intervention affect the mortality rate of a medieval fantasy world? Looking at the numbers, a good-hearted 5th level cleric (probably a pretty standard church leader for a small town or village) would be able to heal wounds and/or bring at least 11 people back from the brink of death from physical injury EVERY DAY, plus a couple extra depending on their wisdom/in-touchness with their god. They could also cure the blind and deaf, the diseased and the cursed. While they could only do these things once or twice a day, the next blind person could just come back tomorrow.
When one assumes that such a cleric would likely have a couple assistants, the accidental mortality rate in our hypothetical town would likely drop to almost 0!
Now, take the high religious adviser to a royal court. Such a high-ranking figure would no doubt have access to Raise Dead, Resurrection, or even True Resurrection spells. While the material costs of such spells (diamond dust between 5,000 and 25,000g) would be too much for your average sod farmer, a regent, whose castle cost upwards of 100,000g would surely have the cash on hand to ensure his/her reanimation in the event of an untimely demise. Assassination suddenly seems far less effective.
Suddenly, it appears more difficult to create a world with a tone like this:
|There's some wonderful filth down 'ere!|
and more inevitable that it will end up like this:
|A little of Moradin's wake-up juice and she'll be right as rain!|
So, what are the options for a DM wishing to mitigate an otherwise sunshine and roses world free of death by anything other than old age or complete disintigration?
Make clerical powers a rare gift: Perhaps most healing in the world is done with alchemy and herbalism. Those with clerical powers are few and far between, making even the lowest-level cleric a truly remarkable individual. This could certainly boost the grit and mortality of your world, but might irk your players if they expect to be able to restock on potions, divine scrolls or get other healing any time they go to town. It would also make clerics a rarity among encountered enemies.
Wear out your welcome: Perhaps even the most healing-oriented gods get irked by repeated requests for healing. After all, they are supposed to be the power behind reality, not just the spigot of life-juice (euphemism!) for the injury-prone masses. If this is the case, would they start ignoring magic-based hostpitals or would they first turn on those who reached their lifetime cap on orc-inflicted axe wounds?
Demanding Deities: Perhaps certain deities have restrictions about the circumstances under which they will heal an individual. Some might only heal their own followers, or might only tend certain types of wounds. A god of war might care less about billy, the kid who got kicked by a mule, and a god of nature might be completely averse to resurrection in any form. Again, it is possible your players could balk at such restrictions.
When you got it, flaunt it!: Let the divine conduit flow strong! Use it as much as your players do. Have town constabularies use "Speak with Dead" to get the descriptions of killers and accounts of murder. Have a feud between kings slowly trying to bankrupt each others kingdoms with repeated "successful" assassination attempts. Create a population problem that forces a good-aligned church into a moral dilemma between letting the mortally injured pass naturally and dealing with an increasingly unsustainable food crisis.
I haven't yet worked out the kinks of this problem, even in my own campaign. If any of you have unique ways that you have used to balance gameplay dynamics with a more mysterious divinity, I would love to hear them. If not, perhaps the ideas I have presented will help shake stuff loose.