Kryptos

Kryptos is an interdimensional criminal from an unknown dimension[4] who appears during the events of Weirdmageddon.

Background
Eons before the events of the series Kryptos indulged in criminal activities before being called together by Bill Cipher, along with 8 Ball, Amorphous Shape, Hectorgon, Keyhole, Teeth, Paci-Fire, Pyronica, and Xanthar.[4]

Season 2
In Weirdmageddon Part 1," during the cold open, Bill introduces Kryptos with the rest of his friends to the residents of Gravity Falls. Afterwards, on Main Street, Kryptos and the others watch Bill turn Ford into a golden statue and taunt Dipper before burning the journals. Later in the episode, Kryptos is seen playing "Spin the Person" and enjoying the "V.I.P." party Bill is having at the Fearamid until Time Baby and the Time Police crash the party. To the beings' delight, Bill vaporizes Time Baby and his squadron. The party then continues as Kryptos and the other beings rejoice over Time Baby's presumed death.

In "Weirdmageddon 2: Escape From Reality," Kryptos and the rest of Bill's minions attempt to leave Gravity Falls to spread their chaos worldwide, only to be stopped by an invisible barrier around the town.

In "Weirdmageddon 3: Take Back The Falls," Kryptos participates in the battle against the Shacktron. Following Bill's defeat, the being is sucked back to the nightmare realm along with its comrades.