The very word “heretic” is a hard one to apply to those Gloranthan cults that are fundamentally grounded in Hero Plane experiences. Now that’s a mouthful, but let me try to explain – with all the Lightbringer cults, Earth cults, Solar cults, and so on, the tenets of the cult are grounded in recurring interaction with the God Time. There are real mythic archetypes in Glorantha, and the cults experience those archetypes routinely through cult holy days (especially on major holy days). Doctrine is based on experience, and what is needed to wield the deity’s magic is set by those experiences – and then taught and reinforced by the temple hierarchy. If you really defy the temple hierarchy you get banned, but it based on what you do rather than what you say.
Within these constraints there’s a lot of range for interpretation. Lhankor Mhy scribes might write things down, but for initiates of cults it is the divine experience. Heresy isn’t really a deal – as an initiate you’ve had the divine experience, whatever it is. You might say shocking things about it, but your initiation is acknowledged as real. It isn’t wrong belief that is the concern, it is wrong action. If you’ve had the divine experience, and still act contrary to the demands of the god – Humakt’s demand for honour and the code of war, Chalana Arroy’s complete pacifism, etc., you aren’t a heretic, but are defying (and not denying) your own experience of the divine. Mortals being mortals, that happens all the time. But it is defiance, not heresy.
For two major religions, heresy matters. One is Malkionism, because it is fundamentally a reason-based approach to the divine. Rather than focus on divine experience, the Malkioni reach towards the Invisible God itself. They don’t experience it directly (except for a very very few – Malkion, Hrestol, etc.) but achieve either Solace that the Invisible God exists and accepts their sacrifice, or Joy in the Invisible God’s presence. Malkioni taught laws of how mortals are to function in the cosmos, and how the individual and social potential, and agency of human beings, is the starting point for interacting with the cosmos.
Now that is a “belief system” as opposed to an “experience system”. We think human society logically should be organized into four broad specialised activities because 1. Malkion taught that, and 2. it is logical. But if I make an argument that really it should organized into three, we can’t go and experience this ourselves. We need to reason our way through it, and our reasoning might be flawed. The authorities might decide we have chosen wrongly and determine that our beliefs are erroneous. That’s heresy, and the Malkioni often worry about that.
The other major religion where this matters is the Lunar Way. Now as Lunar initiates, we get to experience lots of things pertaining to the birth of the Red Goddess, Castle Blue, and her apotheosis. A few very have followed her extraordinarily dangerous path into Hell and returned with experience and power. But the Red Goddess appointed her son, the Red Emperor, to oversee her followers and her interests in the world – that’s the Red Goddess’s instrument in the world. And the Red Emperor holds that the Lunar Way has a purpose and direction. If you challenge that, you are not simply defying your own experiences, but you are defying the expressed will of the Red Emperor – both wrong action and wrong thought. And since the Lunar Way is filled with Illuminates, the Red Emperor treats what you say you believe on accord with what you actually do.
Most of the time the Red Emperor doesn’t care, and tolerates a wide range of discussion. But on certain matters – especially those that involve his own power and role – he’s very sensitive to heresy. Especially if that heresy might damage tax revenues.
So for most cults, if you are initiated, perform the sacrifices and seasonal rituals, participate in holy days and sacred time, and thereby wield the deity’s magic, you cannot be a “heretic”.
If you do things that anger the deity, like blow off cult restrictions or violate vows, you might get visited by the spirits of retribution or even banned by the temple hierarchy. If you do or say things that anger the temple hierarchy enough they might even ban you from their temple. But those things aren’t “heresy”.
None of that is to say that people don’t quarrel and fight over their gods, because of course they do. Orlanth cults have rivalries with Yelmalio cults that sometimes spill over into violence, even if the cults themselves are actually neutral towards each other. But these are between cults, and not within them. And they are often based on shared mythic experiences, that get viewed very differently by the different cults.
But within most cults, if you offer sacrifices, participate in the rites, and experience the god, your quarrels are going to be personal or political, rarely theological.
Dwarf heresies. The main Mostal religion is an unusual one as the dwarfs identify Mostal with the World Machine. They are repairing and reconstructing it, rather than experiencing it. Dwarf heresies are almost more of a HR thing.
Octamonism: “We have a management council of ten for the past 24 centuries, as we have included iron and diamond. You have repeatedly complained about that inclusion, which is damaging productivity. Cease this or be terminated.”
Open-Handism: “Auditing has uncovered that resources or output associated with your project were misappropriated and given to foreigners. Cease this or be terminated.”
Individualism: “You are damaging team dynamics and morale with your false claims that you are unique. You are not. Cease this or be terminated.”
And so on.