Hectorgon

Eons before the events of the series, Hectorgon indulged in criminal activities before being called by Bill Cipher, along with 8 Ball, Amorphous Shape, Keyhole, Kryptos, Teeth, Paci-Fire, Pyronica, Teeth, and Xanthar.[3]

Season 2
In "Weirdmageddon Part 1," during the cold open, Bill introduces Hectorgon and the rest of his friends to the residents of Gravity Falls. Afterwards, on Main Street, Hectorgon and the other 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 Lazy Susan points in his direction and Pyronica happily swallows Hectorgon whole.

In "Weirdmageddon 2: Escape From Reality," Hectorgon and the rest of Bill's minions attempt to leave Gravity Falls and spread their chaos worldwide, but are stopped by an invisible barrier around the town. He and the others later witness Bill's fury over their inability to leave.

In "Weirdmageddon 3: Take Back The Falls," following Bill's defeat, it is sucked back to the nightmare realm along with its comrades.