What other enemies can be introduced though?
Alien invaders? That doesn't fit the theme of the game. Creepers? From Minecraft? Um... Again, doesn't fit the theme of the game. Master chief? From Halo? Again, doesn't fit the theme of the game. Dark peasant? Doesn't fit the theme. Giant kittens? Same reason again. Emoji monsters?! That REALLY doesn't fit the theme of the game.