Very compelling mechanic, casting new spells made me smile quite a few times. It works really well, and feels very exciting to discover.
I don't think I saw much reason to use anything but fire and walls to contain enemies, as these dont need to be very precise - it's difficult to map them well enough to use the lightning. I also think running out of ink wasn't super clear to me immediately, it took a while for me to catch on and better manage my resources.
The look and feel is pretty good but I think it could be pushed to be a bit moodier and atmospheric and witchy, with a more intentional colour palette perhaps. It's well illustrated but doesn't yet feel really designed.
I think enemy health could also have been a bit better communicated. But this is such a cool start, and well worth expanding.