Leonid Meteor

The Leonid Meteor in Final Fantasy: The Spirits Within was the cause of the worldwide Phantom invasion on Earth. Regarded as the nest of the Phantoms, the largest chunk landed on a region in the Middle East and have since spawned Phantoms that threatened the living things on Earth. Other Leonid meteorites also fell on the Arizona Desert and spawned the Phantoms in the American continent.

The meteor has been subjected to many of the United States Military Force (USMF)'s attempt to stop the Phantom invasion. The recent bombardment had managed to wipe out the Phantoms around the meteor, but sooner or later, dormant Phantoms would emerge from the meteor and continued their assault on the planet.

This led to the creation of the Zeus Cannon, which was built with a superlaser cannon that would theoretically destroy the Phantom's nest. While the first shot managed to destroy the meteor, it also exposed the alien's Gaia and spawned more Phantoms into the area. The alien Gaia was finally destroyed thanks to Dr. Sid's efforts.

Real world reference
The Leonid Meteor is named after the Leonids meteor shower that appear in the month of November.