I played until killing the Mindflayer boss, couldn't find more content after that.
I really love the artstyle, the visual presentation in general. Has a distinct personality. The spell book+ items and combining them is an elegant way to theme the inventory.
Some of the early bosses didn't move around much, so I could just stand on spot and DPS-race them without thinking about dodging or even understanding what the boss does. You could have some boss invincibility whenever the player lands a hit.
Maybe add a more distinctive effect when you're hitting something and not dealing damage? Took me a while to notice I had to do something else to defeat that turtle enemy. It'll probably be more noticeable when you add the hit SFX, I suppose.