To trigger this ending, in a New Game+, after defeating Azala and Black Tyrano, go through the gate to 12,000 BC. Use the gate to return to the End Of Time, and use the bucket. Alternately, go to 1999 AD immediately after you get the Epoch for the first time. This unlocks: Tech Showcase - Dual; Treasure Map - Dark Ages (Terra Continent and Zeal Realm).