Hmmm. Can it be? Will someone do justice to this premise at last? There are stories like this by the dosen, but every one I've tried so far has been cursed with various combinations of inane plot, boring characters, shitty worldbuilding and/or bad art. This one hasn't turned me off so far, so keeping my fingers crossed.
Other than that, I do wish they used "monsters" or "magic beasts" or something. I mean, by now it's pretty much a stereotype that those emerge from mana exposure and have magic crystals embedded in them. Unless the author meant literally beasts made of stone?