@WhimsiCat
Magic only being only possible by spirits is also BS, if the human generate the mana itself there is no reason it can't use magic by itself but there are differences like if the mana exists but the spirit is elemental and the human can't change the mana to elemental mana to cause the phenomena it's understandable, raises the questions of "why is it like that?" and "so humans can use non-elemental magic by themselves?", but that is usually fixed by the humans know magic but they can't feel the mana but the spirits can and feed on it, the scenario makes sense because the technological level in these stories is usually very low and no way to feel or harness the mana without the spirits was found yet so acceptable to "humans can't use mana by themselves" because they don't have the minimum needed for it, a way to feel and actively use mana by themselves. No example comes to mind right now...
Magic only being used by some catalyst (crystals, artifacts, etc) is also BS but they have their situations, usually in that scenario mana is not in the human but in the air around it and the catalyst is needed to harness the mana, explaining why it is necessary the catalyst, or the catalyst is used to pay for the magic. Other situations the humans don't have the capacity to use magic normally but the catalyst gives such capacity for some reason but in those cases there are humans that are able to use magic without the catalyst because they trained and learned to feel and use mana by themselves but in a limited way. Example of Catalyst to pay could be Fullmetal Alchemist, can't remember for the others from memory.
Speelword/Magic circle is the human using the magic by itself but needing the transformative system for the mana to accomplish what the user wants. Fullmetal would be an example here too because each transmutation circle does something to the catalyst, from separating the atoms to rebuilding it in the way the circle modify it, another would be Sakura Card Captors in which the circle is used to focus the mana and allow the mage to change it for the effect it want while the cards are specific wills to facilitate reaching the effect desired.
But here it is one entity, God, managing all types of mana, meaning it is possible to transform the mana without needing some elemental affinity, and they can not only feel the mana but also harness and release it by themselves, using accidental magic when it happens, meaning they could replicate the releasing and transformation by themselves but no one ever research ways to do that and no technique exist yet but the possibility is there. There is no reason to not be possible to use magic without a catalyst and releasing mana is something we already know humans can do without it and that is all Myne needs to fight the consuming.
Sorry for the long reply, it was the reason I was not supposed to discuss it as I said. (I'm assuming that you are keeping this to try and get me banned but... oh well.)