During the reign of Lord Dimwit Flathead he became the first to call Quendor "The Great Underground Empire," which became a designation preferred to Quendor. He also renamed the Great Sea as "the Flathead Ocean." Preferring the Eastlands, he moved the Empire's capital to Egreth to Flatheadia.
The rulers following Dimwit did their best to uphold his tradition of excessiveness. The high level of taxation continued, although the money was increasingly spent not on massive construction projects but on extravagant parties and long vacation trips for members of the Royal Family.
During the feeble-minded reign of Dimwit, after countless years of decadence and overtaxation, in 779 GUE the great wizard Megaboz cast a mighty Curse. This Curse killed the Twelve Flatheads and eventually, in 883 GUE, brought about the collapse of the Empire and the destruction of Flatheadia. The underground caverns fell into disuse, coming under the power of the First Dungeon Master; the Royal Treasury was sacked, and everyone moved somewhere else.
The area is now called the Land of Frobozz, after its largest province.