The Flood is a term from Final Fantasy XIV relating to an imbalance between the world elements that causes one to expand and consume a world.
In the past, the Ascians attempted to conduct a Rejoining between the Source and The Thirteenth by increasing that world's darkness. The resulting Flood of Darkness ruined The Thirteenth and turned it into the World of Darkness with its residents reduced to Voidsent, causing the Ascians to rethink their method.
When the Ascians target The First, they exploit Ardbert and his comrades into increasing the amount of light in their world for it to be consumed in primordial light. Though Minfilia Warde stalled the Flood of Light from consuming Norvrandt, it had already claimed most of The First while turning those caught in it into Sin Eaters.
Beyond Norvrandt, the rest of the First is known collectively as the Empty, due to it being scoured by the Flood of Light.
- The Flood concept is influenced by a similar concept in Final Fantasy III.