What would heresy look like in the world of D&D where gods grant followers divine spells, angels and devils visit mortal realms, and powerful adventurers can planewalk through various afterlives? And would there be a difference across editions?
This issue came up recently in my 4e game. There's an anti-clerical populist (the Heresy of St. Ilia) sect which opposes the practice of selling the raise dead ritual (called 'resurgences' in their rhetoric), decrying it as a tool of the elite to stay entrenched in power, a sacred power pawned off to the highest bidder, a denial of judgment for crimes committed in life, carrying even greater weight than beseeching a king to pardon a victim sentenced to die. In part this is a fantasy interpretation of the Protestant Reformation, but I haven't quite hammered out the other aspects of the movement that make it a full-fledged heresy.
Good call.
Although whether or not that is heresy depends on the established norms. It's entirely possible that in other religions and other areas, raising the dead is considered heresy for precisely those sort of reasons. While I haven't approached the subject from that angle, I have approached the subject from the angle of raise dead interfering with the natural order and progression of the generations of and cycle of life. That is to say, when parent dies, his child expects to recieve his inheritance as his right and to take his parent's role in society. When that parent then returns from the dead, it's natural for the parent to see the child as a usurper and the child to see the parent as the usurper. This brings a conflict between the child and parent, an alienation of feelings, that ought not to be. Therefore in my world, many clerics would refuse to raise the dead in this case, and in cases where the inheritance has real legal weight - that is, the heir is inheriting a title of nobility and with legislative, judicial, or magisterial authority, in many countries society has stepped in and declared that it's outright illegal to raise a dead noble to life because the resulting legal problems are too great and tend not to be resolved peacefully when the heir disagrees substantially with the policies of the person he inherits from.
Now, that's not a universal cultural standard. It's a big world. Other places look at the matter entirely differently.
As for heresy in my world, some are more prominent than others:
Gantroism: The premise of the Gantroism heresy is that the gods are not especially worthy of worship. Gantroists believe that the gods are beings much like mortals, possessing greater power true, but even the best of them is capable of error and wrong. Therefore, the reasoning goes, the gods should no more be worshiped than great men, and should be deferred to for the same reasons that mortals are deferred to and no more than mortals are deferred to. The gods have no right to rule mortals' actions, and if they wish worship from individuals, they should strike a bargain with individual mortals.
The first sage to formally postulate the philosophy was Gantro of Corval, who lent it its now common name, but its most famous proponent was Acrocos of Sarman. Some followers of the belief system have been known to distinguish themselves as Acrocosians. There are a variety of other scholars of note who have wrote texts on the subject, and the philosophy has had repeated revivals in disparate regions of the Realms. Some of these writers appear to have arrived at their conclusion independently of Gantro's writings, and the exact teachings of the writers may vary greatly. Some are considered more offensive than others are.
In most of its forms, this is considered one of the lesser heresies. Its followers are not organized, though they do tend to seek out each other's company when they can find it. They tend to be moderate, passive, and intellectual - although some few do try to actively spread their beliefs. Most religions simply consider the philosophy foolish, and scorn its practitioners as guilty of hubris. Secular authorities seldom go further than banning the texts of famous proponents of the theory, and only the most famous and most charismatic followers of the philosophy have ever been executed under the law. Persecution of the heretics is generally left in the hands of whatever deity decides to become offended by the hubris. Such divine persecution is not infrequent, but is generally seen by the Gantroists as proof of the correctness of their philosophy, and the victims of any divine wrath are held up as heroes and martyrs by Gantroists. What persecution that does occur usually occurs at the hands of a mob that does not distinguish the less radical forms of Gantroism from Kelternism.
Kelternism: A radical offshoot of the Gantroism heresy attributed to Keltern the Leper, Kelternism proposes that mortals would be better off if gods did not interfere in their lives at all. It is perhaps the most famous heresy and probably the only one that the average unlearned person has heard of (and certainly the only one such a person would know by its formal name). It proposes that gods treat mortals much like toys, tools, or baubles to be used and played with and that whatever blessings they bestow are not worth the loss of free will they represent and the curses that they bestow with equal pleasure.
Although there are no doubt moderate and passive Kelternists, they tend to keep very quiet about their beliefs because, in the minds of most denizens of the Crimson Realms, Kelternism is invariably associated with Kelternist cultists. Kelternist cultist are highly radical followers of Keltern - perhaps even more radical than Keltern intended - who believe that the best way to obtain the utopian dream of a godless world is to destroy religion and ultimately memory of the gods. They tend to be violent and frequently attack and destroy religious buildings and clerics where ever they find them. As a result, they tend to live quite brief lives. Kelternism is punishable by death in most parts of the Crimson Realms and is illegal in theory everywhere. Writings by Keltern are banned everywhere, and simply owning one is grounds for execution in most municipalities.
Interestingly, some philosophers have concluded that it is likely - whether or not his spirit is currently being tormented by the gods - that Keltern has himself because of his veneration become something of a god himself. However, if this is the case, Keltern has remained true to his principles and has never been known to assist his followers in anyway.
Zhanism: The system of belief expounded by Zhan of Climostra proposes that gods are the creation of mortals, rather than mortals being the creation of the gods as is generally taught. This is of course a radical offshoot of the Existialist theory.
Although Zhanian writings (especially the original works of Zahn) do not necessarily promote anarchy or even impiety (Zhan himself seems to have held the gods in great reverence despite his theories on their origins), in the common mind Zhanians are considered not much better than Kelternists. This is probably do the fact that most Kelternists are also Zhanians, and is therefore assumed wrongly that most Zhanians are Kelternists. Zhanians do not help there own reputation by tending to be very strange. Zhanians are known to encourage the practice the worship of invented deities in hopes of creating new ones. They are known to distribute rewritten stories and religious works about deities whose principles they disagree with the hope of altering the nature of the deity. All of this tends to make it quite illegal to publicly express Zhanian sympathies anywhere with the probable punishment being death most everywhere.
Zhanism is probably unique among the heresies in drawing followers from a wide diversity of ethical and moral systems.
Monoism: A philosophy that believes that there is a single underlying principle to all things, rather than the dualist philosophy widely understood to be correct throughout the realms. Monoists tend to be the brunt of jokes and are considered stupid rather than dangerous in most cases. Monoist teachers are stereotyped as high-minded intellectual sophists whose philosophy is owed to their removal from the every day world. In short, monoists are thought to have no "common sense".
To a certain extent, this reputation is earned. Monoism is most common among sages and is debated generally in language that is so technical as to be incomprehensible to all but specialists in the field. A great many sages that debate monoism are not monoists themselves, and some sages even go so far as to suggest that the study of the great monoist works is essential to developing a full understanding of ethics and theology. The most widely respected monoist writer was Beren of Altair, but the single most famous monoist is without a doubt Verdan the Seer. There are very few monoist cults, but its followers are widely but sparsely spread throughout the realms.
Monoism is tolerated to a certain degree legally compared to other heresies, but teaching it publicly is likely to earn a term in the pillory or stocks. Execution is for the heresy of monoism is rare outside of all but the most lawful minded or most fanatical societies. On the other hand, monoists must endure a great deal of unofficial persecution and even the occasional lynching with little expectation of protection from authorities. Owning a monoist book is not generally illegal but will earn the owner a bad reputation.
Monoism is probably unique among the heresies in that the majority of its followers are lawfully aligned.
In some very neutral regions, a cleric that too strongly emphasizes his own deity over others may be accused of monoism.
Monotheism: Monotheism is extremely rare in the Crimson Realms. While it is not at all unusual for a person to believe or a cleric to teach that one deity is the most worthy of worship, it is extremely rare for a person to believe or teach that only one deity is worthy or worship - much less that only one deity exists. For one thing, the majority of deities represent powers or philosophies that are too narrow to be considered broad powers governing the world. For another, few if any clerics teach that their particular deity is all powerful or even supremely powerful. Finally, it is difficult to argue that a particular deity has a monopoly on virtue.
Nonetheless, despite the difficulty of all these arguments, there are small numbers of people who make one or more of them, and even a few books have been written on the subject. There are several 'All-Father' or 'All-Mother' cults in the Crimson Realms with various philosophies. The most common believes that all the gods are avatars of the single original creator - a sort of monoism. Another, an offshoot of Gantroism, holds that only the original creator is worthy of worship. In addition to these heresies, all the 'All-Father' cults are associated with a certain sort of hubris - that man thinks himself worthy enough to worship The Creator. No 'All-Father' cult has ever been able to manifest legitimate miracles and has a true clergy with divine power. This is attributed, at least by the cultists themselves, to the fact that the true name of the Creator is not known. Quite a few individuals claim to have discovered the secret name of The Creator, only later to be discredited as charlatans or madmen. Many 'All-Father' cults are associated with Kelternists, and even those that aren't are seen as being associated with them. Although no secular power would be so audacious as to explicitly forbid the worship of The Creator, it is generally more than possible to find grounds to execute a member of an 'All Father' cult on some other charge of heresy.
