Pyronica

 is a fema demon and is a interdimensional criminal from an unknown dimension who appears during the events of Weirdmageddon.

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

Season 2
In the episode, "The Last Mabelcorn," the arrival of Pyronica along with her demon comrades arrived into Gravity Falls' dimension is foreshadowed in Ford's flashback of him working with Bill Cipher. When Bill Cipher mockingly tells Ford that he has betrayed him, Pyronica's laughing silhouette is seen in the representation of another dimension projected in the Mindscape.

In the episode, "Weirdmageddon Part 1," during the cold open, Bill Cipher introduces Pyronica with the rest of its demon friends to the residents of Gravity Falls. Afterwards, on Main Street, Pyronica and the other demons watch Bill Cipher turn Ford into a golden statue and taunt Dipper before burning the three journals. Later in the episode, Pyronica is seen playing "Spin the Person" at the "V.I.P." party Bill Cipher is having at the Fearamid. When the calcified statue of Lazy Susan points in Hectorgon's direction, Pyronica happily swallows the demon whole.

In the episode, "Weirdmageddon 2: Escape From Reality," Pyronica and the rest of Bill Cipher's friends attempt to leave Gravity Falls to spread their chaos across the world, only to collide with an invisible barrier.

In the episode, "Weirdmageddon 3: Take Back The Falls," Pyronica participates in the battle against the Shacktron, initiating the attack on its command. Following Bill Cipher's defeat, it is sucked back to the dimensional rift in the sky along with its fellow demons.

Appearance
Pyronica is a pink glowing demon with short pink hair, bangs parted across its face, and several small horns across its skull in between her two other big curved horns. Pyronica has only one eye, just above its wide mouth and thick lips, that hide her buck teeth and fangs. Pyronica has a slim humanoid body, and its limbs are made of white flames. Pyronica wears a long pink cape and pink stiletto pumps.

Quotes
"ATTACK!"

- Pyronica, ordering its demon comrades to attack the Shacktron

"Spin the person! Spin the person!"

- Pyronica while playing "Spin the Person"

Trivia

 * Pyronica is the personification of Bill Cipher's blue flames.
 * Early concept art of Pyronica shows that it was initially going to have snake-like hairs with mouths on the edges, a longer cap, very long hair, bigger and sharper horns, and limbs made of red fire.
 * In a closer final revision of Pyronica, the demon's limbs were to be made of blue flames instead of white.
 * Pyronica's name is a portmanteau of Pyro, the Greek word for fire, and the name Veronica.

Pyronica Пироньяка