Religions of Eberron
Religion plays an important role in Eberron. While the gods don’t physically manifest as they do in other settings, people of faith believe that divine forces play a role in everyday life. Beyond this, shared beliefs help to unite communities and to provide hope in difficult times
Religion is based around the church and pantheons rather than a specific deity. A paladin might thus follow Dol Arrah first and foremost, but still be of the same faith (the Sovereign Host) as a wizard following Aureon. A paladin of the Silver Flame, on the other hand, belongs to a different religion and might have very different views on theological issues, although still devoted to the cause of law and good. Deities in Eberron are not in general specific to a race, although both elves and Kalashtar have religions not commonly practiced by other races.
The Nature of the Gods
In many Dungeons & Dragons settings, deities are beings that player characters can interact with directly. There is no question whether the gods exist; if you're an experienced planar traveler, you can drop by Asgard and beat up Thor. Fundamentally, deities are just very powerful characters.
This is not the case in Eberron. While many of the deities are portrayed with anthropomorphic icons, they do not walk the mortal world or even the known planes. If they exist at all, deities inhabit a higher plane of existence — a realm that cannot be reached with planar travel. Some believe that the souls of heroes travel to this realm after passing through the darkness of Dolurrh; while this is a comforting belief, it has never been proven.
If the gods may not even exist, who do you commune with? Why do planar allies answer your call? Divine magic exists, and most believe that it is a gift from the gods. Something provides answers to commune, and a priest believes it to be his deity. A skeptic may counter that it is the collective unconscious or merely a powerful outsider. As for planar allies, reverence for the gods is not limited to mortals. Celestials and fiends also worship deities. An archon dedicated to Dol Arrah may never have seen the face of the goddess but it believes in her implicitly, and it will aid those mortals who fight in her name.
Ultimately, belief in a deity is a matter of faith. Each deity represents an ideal and espouses a certain code and approach to life. When you embrace the path of a god, you become part of a community in the mortal world. Perhaps, if you are deeply spiritual, you will gain the power to perform miracles of divine magic. This is what people expect of the gods of Eberron: they affect the world by guiding and empowering their followers, not by manifesting and taking direct action.
Alignment versus Belief
One of the major changes in the Eberron Campaign Setting is that a cleric's alignment does not have to match that of his deity. A lawful evil cleric can worship a chaotic good god, and he will still receive spells and granted powers. The main question is what this divergent alignment means. It may be that the priest is betraying the ideals of his church. It is equally possible that the priest fervently believes in the principles of his religion but approaches them in an unusual manner. For example, an inquisitor of the Silver Flame may be lawful evil. He is willing to torture and kill in the interest of what he views as "the greater good," and he truly believes that he is carrying out the wishes of the Flame when he does so. Good-aligned members of the church may find his methods abhorrent, but the question is whether his results serve the goals of the church. In the minds of the people, questions of good and evil are far broader than "what can be detected by detect evil?" When the Silver Flame began its crusade against lycanthropy, the soldiers knew that there were individual lycanthropes that were not evil. But lycanthropy itself — a curse that could corrupt the body and soul of anyone it touched — was seen as evil, and the sacrifice of innocents was necessary to purge the greater darkness.
Pantheistic Clerics and the Cleric with No God
One of the predominant religions of Eberron is the worship of the Sovereign Host, along with its shadow, the Dark Six. Most people worship the entire host and address their prayers to whichever deity suits the needs of the moment. A traveler may offer a prayer to Kol Korran when boarding a ship, give thanks to Olladra after an excellent meal, and make a sacrifice to Dol Dorn when a pirate ship appears on the horizon. Priests typically serve a particular sovereign, but a cleric can choose to worship the pantheon as a whole.
As described on page 35 of the Eberron Campaign Setting, it is possible for a cleric to have no god and still perform divine magic. This is not, however, the same as having no beliefs; it still requires a strong commitment to an ideal or a philosophy. The cleric needs to devise his own system of belief and explain how it justifies the domains he has selected, and the DM always has the authority to disallow a combination of domains. The goal is to allow a broad range of personal faiths — like the warforged developing their own religions — not to encourage players to pick domains based solely on granted abilities.
Divine Magic in the World
Arcane magic is seen as a science. It is a force that can be controlled through formula and incantation. Divine magic is quite different: it is a miracle of faith. True clerics are rare. They are the crusaders of the church, skilled in battle and capable of channeling the power of their deity. The vast majority of priests are experts who possess no spellcasting ability whatsoever. An average religious expert might possess Knowledge (religion), Knowledge (History), Heal, Diplomacy, and Sense Motive, and use these skills to provide spiritual guidance to her community. Most divine spellcasters are adepts, just as most arcane spellcasters are magewrights. A cleric of any level is a remarkable figure.
A side effect of this is that most temples do not sell divine spells. To begin with, many temples don't have a divine spellcaster. Those that do will not sell the gifts of their god for mere gold. If the petitioner is a loyal member of the faith, an adept may aid him at no cost, or the adept may set a price based on the abilities of the adventurer, calling upon him to make a sacrifice to prove his faith or perform a service in the name of the church. The more powerful the spell, the more significant the sacrifice or service. If a nonbeliever serves the cause of the church, it's possible a priest will provide assistance, but a temple is not a marketplace. No one can demand a miracle as if purchasing a spell from a wizard's guild. Needless to say, this makes a character's choice of religion an important decision. A cleric of the Blood of Vol will never consider helping a follower of the Silver Flame, and you'd be soiling your faith even to ask.
There is a notable exception to this rule: corrupt clerics. Especially in Breland, there are priests who are more interested in lining their pockets than serving the faithful. If you can find such a cleric, you can purchase any spell he can cast, at standard prices.