It has always bothered me a bit that D&D clerics work more or less just the same as D&D wizards. Their power comes from a completely different source: gods vs arcane study. So why would they also have spell slots and such? Here is a way to make them feel different.

Spell Checks for Favor

Clerics learn spells per the standard rules, but you can cast any spell you know without regard for spell slots. However, each time you cast a spell, you must roll a spell check to see if you incur your god’s disfavor. This consists of rolling 1d20 against a difficulty of 7 plus the spell’s level, but with a bonus equal to the number of spell slots you would normally have. Any failure raises the difficulty of future castings in the day by 1.

A roll of natural 1 indicates that you have somehow angered your god, and your ability to cast spells is suspended for the rest of the day, unless you do something to appease the mighty deity.

• Failed to keep a dietary requirement.
• Failed to pray at the necessary time.
• Defiled yourself with debauchery, gluttony, drunkenness, etc.
• Broke the dress code.

Appeasement

You may appease your deity and reduce the chance of spell failure by 1 for each act that is specifically determined (by the DM) to be considered favored by your god, such as:

• Destroying an opposing god’s idol or defiling an opposing god’s temple.
• Killing an opposing god’s cleric.
• Foiling a major project of an opposing god’s clerics.
• Significantly promoting one’s own god to the masses by, for example:
  • Building a temple.
  • Winning a major battle in that god’s name.
  • Reclaiming a lost relic or artifact of the temple.

Each time this happens, the cleric’s next spell is a guaranteed success.

Each dawn, the chance of failure increases or decreases by 1 to be closer to 10. For example, if the chance is currently 12, the next morning it will be 11. Or if the chance is currently 8, the next morning it will be 9.

Results

This system makes any given attempt at a spell less likely. But if you try to cast a healing spell, for example, and fail, you may try again the next round, altho the difficulty will be slightly higher.

In practice, this is likely to result in low-level clerics casting more spells, particularly healing spells. So you might add the rule that each successive casting of the same spell in a given day raises the difficulty by 1. So the first healing spell is normal, but the next is at a +1 difficulty, and the next is at +2 difficulty. This would require some play-testing to determine where the balance lies.

Of course, casting a spell in every round of combat will likely eventually lead to a natural 1 and suffering the deity’s wrath, which may reign in players.

Opposing Gods

Depending on how you play alignment, “opposing” here generally means the polar opposite alignment. A lawful good character is diametrically opposed to a chaotic evil character and vice versa. A neutral good character is opposed to a neutral evil one. But a true neutral character is diametrically opposed to no other alignment, so appeasement needs to focus on promoting one’s own faith and not tearing down others.

That’s not to suggest the true neutral druids, for example, shouldn’t tear down evil temples, but that they should seek to tear down those that are actively wrecking the natural landscape, which the druids seek to protect. But this also means, of course, that they can come into conflict with lawful good characters who are also destroying the landscape.