Full name: Flat Monster Age: Ageless Occupation: Soul eater Weapons: hand to hand combat Era: From the Flat World was created Status: Killed Enemies: Flat Boy, Flat Girl, his servants and the citizens.
An ageless demon that lusted for pure power and dictation over Flat World.
Many soldiers were said to have been sent to exile the maniacal demon, he lured Flat Boy in by kidnapping the people of his neighbourhood and Flat Boy's girlfriend.
He sent slaves but Flat Boy effortlessly made it and Flat Boy stabbed him in the heart murdering and crumbling Flat Monster to dusts and ashes.
- He is the only one who has outlived any citizen due to his species.
- He resembles his descendant Tentagon and Browser accept Flat Monster is fully blacked out while his ancestors have colour.