At some point during his life, Elgo, the emperor of Avalonian Empire, discovered the Void and the power of Nil within it. He intended to use this power to gather all the crystals and gain immortality.
The Warriors of Light and Darkness have to travel into the Void to collect several pieces of Dark Matter. After defeating Imperio and Gehenna, the warriors have to go into the Void to find the emperor. Inside the Void, they defeat the Blades of Nil and restore Hope, Trust, Dreams and Love to those who have been trapped inside the Void during the Dimensional Shift. They also defeat the Dark Flow but Vata has to sacrifice himself.
Finally, the warriors manage to defeat the emperor inside the Void and run back to the World of Dusk before a massive amount of Light energy, which was absorbed by Nil, hits them. They are aided by the soul of Gramps, Vata and The Mask.