That makes a lot of sense, I never read Rise and Fall of a Dragon King. Like most every setting that’s been around for a decade or three Dark Sun has some contradictory lore and it’s always really fun to see how different GMs choose to reconcile the lore or invent new lore whole cloth.
In the interest of actually contributing to this thread though since I’ve derailed it more than enough. I actually used my own unique villains for a campaign set prior to the Freedom campaign. It was an entire religious organization revolving around the Sun. Long story short, just because there are no living gods on Athas doesn’t mean people don’t believe in deities. They just tend to base their deities around an element, para-element, or in especially unusual circumstances a druidic group.
(I also depict the Sorcerer Kings as not being too adversarial with clerics, the templar keep a constant eye on any churches and clerics have a very short leash in the city states, but they aren’t killed on sight as long as they don’t oppose the SKs. Though certain cities outlaw rival faiths if the sorcerer monarch is creating their own false god)
The Solari are quite possibly the largest organized faith in the Tyr region. The sun clerics receive immense amounts of divine power and grand boons and in exchange they need to follow only two basic rules. Convert as many to the Solari as possible as they too shall receive Sol’s blessing and oppose the servants of the elements/para-elements whenever possible. On one hand the Solari aren’t actually that bad, their “god” grants his followers notable resistance to his punishing rays and the immense divine power he grants his many priests ensures the faith is well equipped to repel raiders and beasts. The Solari are often even very patient and polite when seeking to convert others and won’t press the issue too hard if it’s clear they won’t change your mind. They offer humanitarian aid to everyone under their protection and all things considered they can seem like one of the best things that’s happened to Athas.
The problem is that they normally only help those that pledge themselves to Sol. Otherwise they will express their grief and regret at your unwillingness to embrace Sol’s guiding light and inform those in need that they are pledged to only offer the resources of the Solari to other Solari. This isn’t too bad, but the issue is the Solari are something of a carrot and stick group. If a settlement refuses to convert they may find accidents begin occurring around town more often, raiders and monsters grow more common, a fire breaks out in a home or field, a well is contaminated. The Solari have the men to drive off the bandits and monsters, the Solari have hard working pious souls to fix your home, the Solari have priests far more powerful than your dour earth follower that can purify the well, if only your town will forsake their false earth god and embrace Sol’s guiding light.
If this doesn’t work or isn’t an option and the Solari feel they can get away with it they will outright sack entire settlements and enslave the population to work on Solari settlements while they take every opportunity to convert them to Sol’s guiding light. It is worth mentioning the Solari are neither blind nor stupid (at least the ones who make any decisions aren’t) and they will not pursue their agenda with a one track mind if it benefits them to take a different approach. They primarily just send missionaries into the city-states as well as personnel to attend to any churches they may be permitted to own where they can oversee worship and provide aid to the faithful. They know full well conflict with even the weakest sorcerer king would spell utter disaster for the faith and earn the ire of the remaining city states. Additionally the Solari have made alliances of convenience with organizations they have no love for if the gains are worth it. This is why they have been able to swallow their bile and assosciate with paraelemental faiths on occasion as well as tolerate the existance of the templarate and even follow all of the templarate’s rules and demands. However, Sol help any unfortunate templar that encounters the Solari beyond the influence of his city-state. Pride is a sin the Solari indulge in all too often and the templar violate that pride all too often.
In the end the high priests of Sol all have their own personnel agendas and desires and each of them is a very high level thanks to Sol’s generosity. The only thing Solari high priests have in common is they are all willing to follow Sol’s dictates in exchange for the vast power he grants them both through divine power and through their influence over their fellow Solari. This perpetuates the organization’s agenda, for as the Solari grow in numbers both Sol and his high priests benefit.
For the record I made a notable religion for every element and para-element if folks are interested in the others. The four elemental faiths each have their own core belief on how Athas can be made a better place for everyone. The four paraelemental faiths tend to more actively focus on what their “god” can do for you the individual.