Hectorgon is a red hexagonal demon with arms, big tangerine lips, a mustache, a bowler hat with a gold rim (Light blue in this picture), and a light blue tie. Hectorgon has a small red aura.
Eons before the events of the series Hectorgon indulged in criminal activities before being called together by Bill Cipher, along with 8 Ball, Amorphous Shape, Keyhole, Kryptos, Teeth, Paci-Fire, Pyronica, and Xanthar.
In Weirdmageddon Part 1," during the cold open, Bill introduces Hectorgon with the rest of his demon friends to the residents of Gravity Falls. Afterwards, on Main Street, Hectorgon and the other demons watch Bill turn Ford into a golden statue and taunt Dipper before burning the journals. Later, Hectorgon is seen playing "Spin the Person" at the "V.I.P." party Bill is having at the Fearamid, until a calcified statue of Lazy Susan points in the demon's direction and Pyronica happily swallows Hectorgon whole.
In "Weirdmageddon 2: Escape From Reality," Xanthar and the rest of Bill's minions attempt to leave Gravity Falls and spread chaos across the world, but are stopped by an invisible barrier which makes Bill considers getting Ford 'out of retirement'.
In "Weirdmageddon 3: Take Back The Falls", he did not participate in the battle against the Shacktron. Following Bill's defeat, he was sucked back to the nightmare realm along with his fellow nightmares.