Spells are like everything else in the universe - they work with ENERGY and LIGHT. A spell by a sorcerer or a spell by a witch, use the same energy but in a different way - but it is all "energy being manipulated and bent to suit the needs of the wizard or witch."
REVENGE SPELLS
"A revenge spell has the energies of all 3 people in the spell." The power of the witch is to bend the energies of both the other parties to create an ENVIRONMENT OF REVENGE. The witch doctor will suck from your hatred, and desire for revenge, and warp it, or bend it toward the person you seek to hurt. While this may seem easy enough it can be VERY DANGEROUS for all 3 parties. Once the spell is energised by intent to harm, it will seek out and fulfill the intent. If the person you are trying to hurt has more power than your witchdoctor, or has a POWERFUL PROTECTION SPELL, this "HATE ENERGY" or "REVENGE ENERGY" needs to go somewhere - it cannot just disappear. The revenge spell goes where there is least resistance, not to the witch doctor, because he has power to avoid it, "but back to the person who is seeking revenge." The spell backfire on you and you will end up being hurt by your own revenge.
FORGIVENESS SPELLS
It takes a very powerful witch to craft powerful revenge spells. A witch or witchdoctor who knows what sorcery is all about, knows this. "A practitioner that has any sense of responsibility will make the dangers quite clear to you." They will first seek every opportunity for you to resolve the problem without magic - often a better spell is a FORGIVENESS SPELL - this may be the type a spell you will learn in sangoma training, as sangomas work with good energy, and "serve their people - not their pocket."
Reference: witchcraftforall.blogspot.com
