This concept is genius, I love the idea of placing monsters and trying to stop the hero.
Unfortunately the UI was really buggy, it was super hard to actually click the monsters to place them, and it kept dragging the screen around instead. Also, I couldn't really tell what was happening during the battles against the hero, I was pretty much just clicking the dice roll and hoping for the best. Simplifying that at first might help.
Overall, it seems like a really cool start to something awesome. Good work!