I've come here to state something simple, which I think is profoundly important. No spell is impossible. It's merely the amount of power required, or in most cases, the reputation of the writer.
For example, a while ago, I found a cat transformation spell on the YouTube. It was poorly made, had several.. immature people in the comments. The type of people that believe anything they see. However, this spell actually worked quite well. It allowed me to accomplish what I had not done before: Feeling the animal I wanted to be, in more places than one. Not very practical, but it says something.
I had discovered something within at that point. I had discovered that true magic can be really any sort of spell. The reason most of them t work