orgetful spells are from a group of what is commonly called life spells
. We all forget things from time to time and these spells focus the power of distraction and rememberance to help us forget things we do not wish to remember (like of lovers) or remember things we have forgotten (like where the car keys are).
It is said that those of great power can cast such great forgetful spells that they cause their enemies to forget everything about their lives and their pasts. It is said that once so much power has been gained by an individual that the person usually casts the spell on themselves because they have then gained pure absolute knowledge and wish to forget.