Oedipus and evil

There is not much to go with Oedipus and evil but there are a few things that could be interpreted as having an evil or twisted side. Oedipus is not an evil or bad man, he is quite the opposite although he kills his father and marries his mother. He was blind to the truth, but then could the truth sometimes be evil? I am aware of the quote of "truth will always prevail over the forces of evil" but is that always true? Can evil take the role of truth and end up twisting what is true? Why do we imply that truth is always good and lies are always bad? The Sphinx is also portrayed as an evil creature who eats the people that cannot answer its questions but is the Sphinx actually evil? They are creatures of knowledge and only ask questions, if you cannot answer it then it eats you. Is it really that evil? or does it encourage you to learn and be intelligent? There are also the gods and fates in Oedipus which can be interpreted as evil. The gods let Oedipus suffer throughout the story while they sit back from afar and watch. Can gods be evil? To let people suffer and go through hell or do they actually deserve it?