You have the wrong one the demonic flower(the black eyeball one) turns a person into a demon u need the blue lily flower which can be found(starting direction at least) when u go left or down i don't remember exactly
I do not know if u can switch between the two forms but the demonic flower should be within the dungeon near the witch and use the corrupted compass to find the flowers(or look in harus little spot you can access it by making progress in her relationship)
