Kryptos

Kryptos  is a character in Gravity Falls, appearing in the episode "Weirdmageddon Part 1." He is an old friend of Bill Cipher and is part of The Gang of Interdimensional Criminals and Nightmares. He was, along with Bill and the rest of the gang, trapped in a decaying dimension, but was finally set free when the rift between the dimensions cracked during the prophicised Weirdmageddon.

History
Kryptos has unknown criminal history.

He was prisioner of a dimension for trillion of years craving to leave it and have fun at last.

Season 2
In "The Last Mabelcorn" Kryptos can be heard cackling and cheering in Ford's flasback, inside of his dream dimension, through a rip made by Bill, as the latter reveals his true intentions.

In "Weirdmageddon Part 1" he is finally set free from his dimensional prison and stands along with the rest of the gang until the party starts.

Inside the pyramid, in the heat of the party, he can be seen dancing and drinking with the other demons, and when theTime Police crashes the party and the Time Baby is killed, he is worried, but the worry turns to malicious excitement, as the party gets on.

Appearance
Kryptos is very similar to Bill, as in he is also a floating shape with black limbs. However, he is a black rhombus, and the top perimiter of his shape resembles a compass, with a functioning eye at the turning point, and the bottom perimiter resembles a square ruler. Additionally, he has a big wide mouth with buck teeth and wars blach gloves.

Trivia

 * His design is heavily based on the Squares and Compass symbol, a symbol associated with the Illuminati.
 * He is the second character to be based on an Illuminati symbol, the other being his friend Bill Cipher, who's inspiration is the Eye of Providence.