I once heard a story of a world build purely on light, which made it so unsustainable that it crashed. So maybe it is our perception of darkness that suffers our light? Just a thought. For me white magic is the restriction to only do good, and black is to not set any restrictions to what you might attract. In this sense I think you could define something as dark mediumship. In some sense you could say you only use a crutch as long as your leg is broken... not sure if my ramblings make sense
