I like the concept a lot! The assets and visual style are nice, too!
I felt like the game could use some adjustment, though.
The first thing that came to mind for me was that as a tower defense, especially one where the narrative theme is "build a kingdom," the mechanic of placing towers is too messy. You end up with a pile of overlapping sprites that you probably failed to put where you wanted to in the first place.
That leads me into the player character movement. The game is relatively unforgiving in terms of how easily you can lose. That isn't necessarily bad in itself, but if you're going to do that, you need to at least empower the player with the ability to keep themselves alive through skill. I felt like the movement was extremely difficult, delayed, and didn't react the way I wanted it to most of the time. So when I lost my HP because I clicked 2 seconds ago and the character didn't go where I wanted it to, that's really frustrating!
I agree with some of the other commenters on enemy variety and scaling, too, but I feel like content just takes time, which you all likely didn't have in the jam. Overall, though, it is a good idea and submission; I could see myself playing a lot of it with some tweaks in the correct direction!