We tend to keep things simple at Thoth and say ‘Black magic is when you purposefully go out of your way to use magic to F**k someone or something up.’ This could be a specific person, group of people, or perhaps even organisation or company.
You may have heard many New Age, fluffy philosophies when it comes to the practice of Malificent, Baneful or hurtful magic, but ultimatly it is for the witch to decide what ethics they apply to their magical practice. If you decide to work magic on someone then you need a well thought out spell so it doesn't backfire.
Spells are packedged up forms of energy which have been programmed to do something. Energy can always be transmuted, but you need to know how to do this. If a person you cast a black magic spell on understands this, then yes they can send it back to you or neutralize it, but only if they understand how. Black magic spells work best on mundanes (muggles) who don't know witchcraft. I wouldn't suggest working this type of magic on another witch as you might get more than you bargained for.
All of our spell kit tins come with a mini booklet designed to explain how different types of spells work. This booklet can be unfolded to reveal two different spells to choose from. We prefer to give people two options as not all spells resonate with everyone and so you may gravitate towards one or the other.