This is a great submission that certainly keeps you playing! The discovery of skeleton archers was exciting. I also loved when I would clear a section of town with one mob and be joined by an even greater mob that grew itself fighting nearby. It makes you feel that something is really kicking off.
The carefully placed crowds cause you to properly infiltrate the people before unleashing your wrath if you really want a big mob to start with. This creates a great atmosphere as you stroll into town hooded and cloaked watching the children run happily in the road, thinking "if only they knew". I rate this game ARMAGEDDON/10
You may want to give the player a super short tutorial and introduce them to a few mob types upfront to encourage them to clear levels and progress. There is depth here!