Good and evil are fact of life. The gods and demons are real, and they wage war against one another for control of reality. They are led by champions, Lords of light and dark, and they have been fighting for a very, very long time.
Humans are not evil, nor are they good. They are lesser beings, yet because of this they have true freedom in a way that gods and demons can never have. The same can be said for myriad other races that live on the earth. The power to choose, the will to act against one's nature, to be more than nothing. To be good or evil by one's own will, that is a power beyond even the Lords themselves.
The Lords power is immense, but their minds are greater still. They have perfected warfare beyond any art or philosophy known to mortal beings, to the point that any battle between their forces is guaranteed to be a stalemate.
This realization marked the first evolution of war.
Many evolutions later, the Lords and their servants wage war in strange ways. They beguile and ensnare, they seek to recruit the free beings of the world to serve them, and in doing so to grant them the power needed to overcome their enemies in victory.
It is in this world that Harry Potter was born, and in this world that he fought, and in this world that he died. Some say he was noone, a product of chance. Others claim he was engineered by man, the culmination of generations of secret plans and careful stewardship. None can say for sure.
What is known is that he waged war, not gods, not on demons, not on mortal beings, but on all three. For the sake of the free beings of the earth, he wiped out the Lords and those who followed them, eradicating them to the very last of their kind.
A free world, bereft of true good and evil, left now only to the power of choice. This is the legacy of Harry Potter.