>>104231471
Viti magic has worked a bit differently from Vitubia's, in general it's more powerful and versatile. I like to think it works on the same fundamental principles, but the leylines of Viti just have more mana running through them or something like that. But yeah, it seems pretty common to have most divine's magicks do some basic magical tasks, like glowing, powering mechanisms, or communicating with the spiritual, and then the specific essences can have various unique effects. I do think different essences wouldn't be a drop-in replacement for another; it'd be like having a machine that runs on 12 volt batteries and expecting it to still work if you swapped in a 24 volt battery, or a fuel cell. A skilled magical craftsman could maybe make a conversion, but it'd take some work.
As for how hoomans deal with the trade of magical goods obviously that's up to you, but if there are regulations on this market you might see a black market of illegal magical goods dealing arise, which is always fun. that could tie into how those cults fund themselves and an added reason for them to stay underground.
Oh man I love spec bio, looking forward to that. I wrote a little bit about morig spec bio in the zoology story.