In reflecting on the theme of the origin of evil, one finds the great sagas of Gods and Heroes. If we have texts, we have to have a vivid imagination to perceive the meaning of the saga. For instance the figures of Hera and Zeus. They easily remain just names, if we don't try to experience them as intense as we can.
In the forms of art we find marvelous help to animate our images. Artists have the faculty to make perceivable what is the deeper meaning of such figures in for instance mythology.
Music is perhaps the most impressing way to animate our feeble thoughts and feelings. And we can think about Richard Wagner whatever we want - we should however think about the fact that he lived and died long before the 2nd world war - Wagner was a master in articulating into the finest details the acts and emotions of persons - whether gods or human beings. He handles his theme with great courage. He achieves, by the slowness of action, that the tension is not evoked by speed, but rather by extending the actions. And the music gives it the tension, the emotion, the dramatic undertone.
In the Valkyries the old German mythology is shown. In the most moving way the division of the God Wotan and his dearest child Brünnhilde is painted. In the dramatic scenes it becomes clear how everything on earth, between people, is guided by the Gods. A man can think that he conquered an enemy - it is only because, while being brave, he got help from the Gods.
The bravest men are guided to the Walhalla, after their death on the battlefield - and the guides are: the Valkyries. Daughters of Wotan, riding in the air, and coming to earth only to guide the dead to the Walhalla, where they may join the other heroes and live with the Gods.
The Gods judge who has to die - the Valkyries accomplish whatever the Gods decided.
And now comes this deeply moving scene, where Brünnhilde knows that her father Wotan wants to keep a man - Siegmund - alive, but his consort Fricka doesn't allow this, and he has to give way. Brünnhilde has to accomplish the defeat...
But as she sees the earthly deep love of Siegmund for Sieglinde, for whom he even rejects the Walhalla, she decides to rescue him - in full consciousness that she acts against the will of her Father, the God.
This act of freedom marks the beginning of the 'Götterdämmerung', the Twilight of the Gods. Wotan himself has to act instead of Brünnhilde and makes Siegmund die anyway. After that he has to reject his dearest daughter, and throw her on earth, between the human beings.
This moment, the first time a Goddess does something by her own will, is very impressive, because it is clear that the motive is perceiving true love between human beings. One cannot possibly say that Brünnhilde is committing a sin - and still she does. Here the mystery of the origin of evil emerges, where we can see, that evil can be a good and good can be evil... It is only evil, because it is not covenant with what is custom, and it can be good because it is based on true love.
But we have received a mind and a heart and we are allowed now to judge ourselves about good and evil. And when we look carefully at ourselves while judging, we will find a true sense for truth in our minds and our hearts. Brünnhilde shows this for the first time.

Arthur Rackham's illustration to The Ride of the Valkyries.
The Valkyries by Mieke Mosmuller