Sorcery is the third major magic system, after spirit magic and Rune magic. It is fundamentally concerned with understanding the source of everything and the ultimate principles underlying reality.
In the core RQ rules we get a smattering of sorcery – basically because of course the followers of the God of Knowing have learned some sorcery. But sorcery just isn’t that big of a deal in Dragon Pass or its surroundings.
It is in the Gloranthan West (Seshnela, Safelster, and Fronela), in Kralorela, Teshnos, Umathela, and Fonrit that sorcery really comes into its own – the domains of the Middle Sea Empire. We associate sorcery with the Malkioni, but it is also known in Kralorela and Teshnos.
There are hundreds of sorcery spells. Some are logically arranged together as an organized philosophy, while others might be tied in deeply with an understanding of martial arts and emphasize harmony between body, mind, and cosmos. Some spells are widely known and are self-sufficient like Dormal’s Open Seas spell. Others require significant theoretical underpinnings to understand and cast.
And of course the Irrippi Ontor cult has sorcery. But like with Lhankor Mhy, it is not nearly as big a deal in the Lunar Empire as spirit magic, Rune magic, or Lunar magic.
The Opening spell can be learned and used without any background in sorcery, is this common, or is it a special case? I suspect there are many such spells, especially outside of the Malkioni. The Malkioni consider them intellectual dead ends but like with the Opening spell they might be the only way to get that result, dead end or not.
In the end, a sorcery spell is just a learned skill that has a few fixed prerequisites.
Is there still Red Goddess hybrid spirit magic / sorcery? yes. But it is not actually a hybrid – it is its own thing.
Why didn’t you go with the RQ3 sorcery system (like in Strangers in Prax)? Greg and I didn’t think it was Glorantha. It was far too generic, and did not in anyway interact with the setting and its themes. If you wanted to use it for some other appropriate setting, it could be fine.