Silla existed within the galaxy as a planet characterized by its moderate climate and abundant forested regions. A tranquil and unhurried world, Silla's landscape was composed of grasslands, mountains, and forests. The planet's inhabitants resided in small villages scattered throughout the grasslands.
In the galaxy during the time of the Imperial Era, the Imperial vessel known as transport 904 experienced a catastrophic crash on Silla, leading to the escape of its cargo: a cloned specimen of a Zillo Beast. Clone Force 99, a group of renegade clone troopers, landed on Silla with the intention of salvaging the crashed ship, but they were unaware of the creature that had been onboard. Upon discovering the Zillo Beast, they were forced to retreat. As the beast went on a destructive rampage, the residents of a nearby village were gathered up and taken away.