Zuul

"I am the Gatekeeper."

- Zuul to Vinz Clotho. "There is no Dana, only Zuul."

- Zuul to Peter Venkman while in possession of Dana Barrett's body.

Zuul the Gatekeeper is one of the two main minions of the powerful demonic being known as Gozer and one of the main villains of the original Ghostbusters movie, and she and her male counterpart Vinz Clortho are part of the demonic race of hellhounds known as Terror Dogs. Zuul is known as the "Gatekeeper of Gozer" and is considered by many to be a female entity due to the fact it possessed a female victim and its role as the "Gatekeeper".

History
It was worshipped by the Sumerians and Hittites in 6000 BC, along with Gozer before he and his followers were overthrown by the Babylonian goddess Tiamat and her followers and thus banished to another dimension.

Centuries later, Zuul rewakens from its statue-like hibernation after its spirit was seen at a strange temple within another dimension by Dana Barrett from her refrigerator at her 55 Central Park West apartment. Zuul later possessed her and sought out Vinz Clortho, the Keymaster who had likewise possessed Louis Tully's body - the union of these two monsters would spark the necessary power to release Gozer into the mortal world and begin the apocalypse.

Zuul burst out of Dana's kitchen door as demon claws had her pinned to her sofa which then slid into the kitchen where The Gatekeeper attacked and possessed her.

While possessing Dana's body, Zuul was able to speak, but could not access Dana's memories or knowledge. She took on the identity of The Gatekeeper and proceeded to wait for Vinz Clortho The Keymaster, another minion of Gozer who had possessed the body of Louis Tully, Dana's neighbor. Lying in wait of The Keymaster, Zuul was visited by Peter Venkman, who had arranged a date with Dana Barrett prior to her possession. Peter noticed her radical change and attempted, unsuccessfully, to talk to "Dana", who instead became angry and frustrated. Zuul (in Dana's body) spoke in a demonic voice before concluding their date by levitating and growling monstruously at him.

When Walter Peck shut down the Ecto-containment unit, The Keymaster managed to escape and find The Gatekeeper at Dana's apartment, the two demons shared a passionate kiss and went to the rooftop where they were later finally able to mate. Post-coitus the demonic couple opened the gateway to the Temple of Gozer, transforming afterwards into their true demonic Terror Dog forms before taking their place next to Gozer, who entered through the gate with the intent of destroying the world.

After Gozer was defeated by the Ghostbusters, Zuul disappears from this dimension and Dana Barrett is transformed back into a human being, having no recollection of the events that took place since her and Louis' demonic possession.

Despite being a minion of Gozer, Zuul enjoys quite a large fanbase and the name is well-known even to those who are not active Ghostbusters fans due to it often being parodied or referenced in other works.

Trivia

 * Zuul is referenced in What in Samhain Just Happened?! on page eight. Janine's Car's license plate reads "GBI ZUL".
 * On page 17 and 19 of Ghostbusters Issue #3, Zuul is referenced by Idulnas and in the Spates Catalog entry for Idulnas. It is said Idulnas' power eclipsed that of Zuul.
 * Zuul is a part of one of Nostalgia Critic's running gags, whenever the movie he reviewed introduced a demonic creature (usually dog-formed), he would mimic Zuul as if saying, "ZUUL, MOTHER**KER! ZUUL!!" There are several variations of the gag.