The butterflies were actually made on a whim to test the AI.

I picked a butterfly sprite and made it approach the player and then move into a random direction, then repeat. This resulted in a sort of erratic flapping motion that I just fell in love with. I knew that I wanted to implement that behavior in the final product. For most of the demo's development there was one butterfly, but then it hit me: "have the butterflies act as a sort of esoteric hint system." Butterflies will be a common entity throughout the game and it fits well with the themes that are present already. 

I may apply the butterflies AI to the bat enemies in order to create an easier starting enemy and make the spirits harder. I already have some ideas for how to implement a new mechanic that will make scaling enemies late game simpler for me.