Everybody is always deceived by the fact that they can suppress the inevitable. They always assume that once it disappears it is gone forever, that one victory wins the war. I cannot tell you how wrong that is. Darkness and evil are like a virus that attacks the human body. It will destroy it to the point of near death, and as the body thinks all hope is lost, a cure is created just in time. Then the body tricks itself into believing it will never come back. When actually, the cure only makes the virus fade into the background. There it will wait until the body forgets that it ever existed. Then the virus springs back up and the process starts all over again. This cycle of death and destruction will continue until a cure cannot be found in time, and the virus achieves its ultimate goal, death. Darkness has only one master and that is of who has been in the shoes of both sides and feels both sides pain and want. This being has the key to destroying one and forever saving the other. The path that one must take holds pain and grief which would make the mightiest of heroes cry to their mothers. This path always ends in tragedy and peace. This is the path of true heroes.
Azeroth was infected with the same virus, the Burning Legion. It was taken to the very edge of life and nearly fell, but a hero rose amongst the men and was saved. This is the hero we will follow from his rise to power to his heroic demise. This was a true hero.