The Water Entity.
The Water Entity (異次元の水瓶, Ijigen no Mizugame?) is a powerful artifact created by Xagor in Final Fantasy Legend III. It resembles a gigantic urn atop a floating cloud that continually pours out endless water into the ocean by which it slowly floods the World. The Entity could be located significantly to the northeast of the Palace, north of the island that would one day become Viper City.
It also poured forth savage monsters without numbers that proceeded to invade the world, the monsters systematically sacked the towns of the World searching for the Talon units. The level of the oceans rose at a frightening pace, and the people fled inland. As time progressed the Water Entity had flooded almost the entire world and would eventually make life intolerable for humans in the future, this prompts the main characters of the story to go on a time-traveling adventure to find a means to defeat the Water Entity. Along the way, they would discover the truth about its origins.
The Water Entity was ultimately destroyed by a dying Sol. With its destruction, the mass flooding of the world was undone and the monsters stopped invading. The Water Entity itself was not a sentient being, but rather a mystical construct.