Nice name for the game ;)
More seriously I think the game is great (keep that in mind while reading this comment) but I found some bugs: The number of coins (images) displayed on screen doesn't correspond to the number of "coins left" (text). When there are multiple knights and that one of them die, everyone stop fighting, or at least they deal no damage even though the fight animation plays (it happens rarely, I couldn't reproduce the bug on command, sorry :/). When you restart after you lose, you keep the progress of the previous game.
The game is quite easy if you farm money during the early stage, at some point you earn more money than you can spend (even with spamclicking arrow) and with enough attack upgrades, with just one basic minion you can solo all the knights of a wave.
Also the the art looks great :)