Three Doors are all that stands between Apocalypse and the rest of the world. A series of obstacles must be completed before each door can be opened.
Once the First Door is opened, it is followed by The Second Door that has a picture of a giant spider on it. Before it can be opened the Mystical Arachnid must be found and destroy, because it was created to guard that door should anyone ever decide to awaken Apocalypse. The door will then instantly open.
This followed by the Third Door.