Gozer the Gozerian
Gozer the Gozerian was a god worshipped in 6000 BC by various primitive cultures including the Hitites and Sumerians. It was an androgynous, sexless being capable of assuming whatever form it desired. Gozer was possessed of many aliases throughout the centuries, including Gozer the Destructor and Gozer the Traveller. A modern-day worshipper of Gozer, one Ivo Shandor, conducted rituals on the rooftop of a building located in New York City sometime after World War I, with the intent of bringing Gozer forth into the human realm to destroy it. Gozer had two faithful minions/pets, the Terror Dogs Zuul and Vinz Clortho, whose carnal union in the bodies of chosen human hosts (Dana Barrett and Louis Tully) was to be the tool by which the gateway to the spirit realm would open, allowing Gozer to appear.
When Gozer did appear, it was in the form of a beautiful young woman with blood-red eyes and short black hair. "She" confronted the Ghostbusters, and at first assumed them to be fellow gods. Especially when Ray Stantz ordered the deity to return to its realm of origin. However, when Stantz answered no to Gozer's inquiry, the enraged god electrocuted all four of them with bolts of powerful supernatural lightning from "her" fingertips, very nearly sending them flying off the roof of the building. The Ghostbusters proved tenacious foes however, and attempted to capture the god with their particle throwers. However the nimble Gozer avoided their beams easily and ultimately vanished, manifesting thereafter as a disembodied voice commanding them, "Choose the form of the Destructor!"
Despite having the ability to assume any form it desired, Gozer seemed to take a sadistic pleasure in forcing its victims to choose what shape it would take when it destroyed them. Ray Stantz ultimately chose Mr. Stay Puft, figuring that the jolly children's character would be harmless, only to have Gozer reappear in the form of a 200-foot-tall version of the famous marshmallow man! After terrorizing the gathered crowds of New Yorkers and stepping on a few parked cars (not to mention a church), the marshmallow monstrosity was set alight by the Ghostbusters firing into it with their particle throwers, and the flaming beast then began to climb up the side of the building to get them. Unfortunately for Gozer, by the time it reached the roof, Egon Spengler had already thought of a way to shut the gateway through which Gozer had come, and the resulting explosion completely destroyed the marshmallowy form Gozer had taken.
Exactly what became of Gozer after this is unknown. Being a god and thus immortal, it is unlikely that Gozer was permanently destroyed, and instead merely returned to its original realm to await another opportunity to escape into the human world.
In the script for Ghostbusters, Gozer was originally to have appeared in the form of Ivo Shandor instead of an anonymous woman.