I think the concept is fine, though I find it hard to predict how shadow element changes. Sometimes it follows whatever element I use, sometimes it gets stuck on whichever element it had earlier. Other than that, the variety of spells was nice, but in practice I preferred to opt for a single-element build, in part because I couldn't tell how shadow's elements worked, and in part because it was too much thinking on top of trying to target down the enemies following me.
The gameplay felt a bit clunky - part of that may be my laptop not being the demon of the speed, so the framerate would be pretty limited? But also I felt like the second area in particular was really cramped, and on top of that I'd sometimes get stuck in a sneaky corner. Sometimes I also wouldn't see enemies that were right next to me, and there didn't seem to be auditory feedback for their melee attacks. I feel like having the game follow the third person perspective could alleviate some of these issues, as I'd be able to see nearby walls and melee attackers.
Still, I enjoyed casting spells here and there and the variety of upgrades was nice. I won't judge the assets, because by your own admission they were mostly external ones. Still, it's pretty nicely put together, I just wish the game (especially the second area) was a bit more spacious, to give better opportunities for outmaneuver the enemies.