Good lord I don't know what is wrong with me, but I couldn't rest until I found the damn elixir after defeating everyone hah.
It looks really easy at first and then you just die on the second part of the island. I only noticed after my fourth defeat that I had some lights on my body and could put them out against the water. Not an obvious mechanic, but when I realized it, I just went through the game crushing all the little people like I was some villain from Attack of the Titans. It's addictive, thank you! :D