Corruption magic is curious and not well-documented. This is because, when compared to death art and blood magic that can be performed by anyone with a damaged moral character, corruption magic requires a connection to a god.
Although there are many lesser gods, they generally do not choose to bind themselves to humans. In fact, a naive reader might wonder why it is considered "corrupt" to have a human bind themselves to a god?
Humans and gods are not meant to be intermingled so closely, and the act of doing so drives both of them insane, or so it is said. The impure and changing nature of a human and the one-sided archetypal nature of a god do not mix well.
Still, corruption magic has reared its head throughout history, and some of the less savory lesser gods have sought this unholy union many times in the past. Its result is an evil human of incredible power, who, through the use of their power becomes more and more corrupt and gains yet more power, until finally their soul is devoured and the god takes their place in the mortal realm.
Needless to say, these events have been few through history, and have always been bad.