8 hours or 8 days? Damn, i too use js but I am not as skilled :(
The game is really fun, and have 13 different enemies is a good, challenging task.
My suggestions are:
1) Work on the music and variety of sounds, those are quite important for atmosphere
2) I liked the possibility to challenge each enemy one-on- one (or couples, or 3...) but all of them were really a breeze. You could easily add more levels with enemy combinations to make it more challenging, or nerfing some overpowered skills like vampirism.
3) A little bit of plot development would help, while playing I was thinking... why sending a peasant against you?