Fearamid

The  is a giant pyramid summoned by Bill Cipher as his castle and lair during the events of Weirdmageddon.

History
In "Weirdmageddon Part 1," during the cold open, Bill promptly summons the giant pyramid in order to establish his new found dominance over Gravity Falls. Later, Bill invites his demon friends to a "V.I.P" party in honor of them conquering Gravity Falls' dimension. However, during the festivities the Time Police along with its leader, Time Baby, crash the party stating that Bill's tampering with the town's dimension "could destroy the very fabric of existence." Despite their efforts, the squadron, including Time Baby, are instantly vaporized by Bill, leaving as the only survivors Time Baby (who according to the episode's cryptogram will regenerate in 1,000 years) and Blendin Blandin, who makes a narrow escape from the Fearamid.

In "Weirdmageddon 2: Escape From Reality," Bill is sitting on a throne made from stoned people. He then announces his plan to spread weirdness across the globe.

Appearance
It resembles a large dark red-brown pyramid with the top detached and multiple bricks and broken off pieces floating around it. In the cracks and lines, there is an orange-red color which resembles lava. These lines however flash neon colors to the beat of the music as Bill and the others party within. The interior is black with neon, rainbow lines around the bricks which also appear to flash with the music. There are stairs seemingly leading to nowhere, and a large, red stained-glass window which resembles an eye with a slit pupil. Bill's "throne" is also in the room, which looks like a black and rainbow-lined pyramid with the top missing and two stairs lining the bottom.