Vilosoria, a planet of the Mid Rim, was located within the Lifh sector. It served as the original homeworld for the Vilosorian species. This species exhibited a unique trait: their behavior shifted between peaceful and aggressive carnivores depending on the planet's seasonal changes. The Galactic Empire invaded Vilosoria and established a garrison. Subsequently, during the Galactic Civil War, the Rebel Alliance droid R2z-DL provided crucial intelligence to pilot Koedi Raef. This information included details about Imperial activities in the sector, the patrol patterns and mechanical failures of the Empire's Interdictor cruiser Fireclaw, and the Vilosorians' seasonal transformations. Raef strategically used this data to misdirect the Fireclaw, isolating the Vilosorian garrison. The Alliance then assisted the transformed, carnivorous Vilosorians in liberating their planet.
Situated within the Vilosoria system, Vilosoria was a terrestrial planet. This system resided in the Lifh sector, which was part of the Slice region of the Mid Rim. The planet experienced distinct seasons, including winter, with its cycle alternating between cold and warm periods.
The Galactic Empire once launched an invasion of Vilosoria, establishing a garrison. However, shortly after the Battle of Yavin, the Rebel Alliance astromech droid and spy R2z-DL, who was working undercover on the Bortele sector planet Hypotria as a starship maintenance droid, acquired Imperial codes. He also gained information about the Empire's supply routes in the Lifh sector, the patrol routes of the Imperial Interdictor cruiser Fireclaw, reports on malfunctions affecting that vessel's gravity well projectors, and a description of the seasonal changes experienced by the native Vilosorian species.
R2z-DL concealed this information within a data packet stored in the memory banks of the Y-wing starfighter flown by Alliance pilot Koedi Raef. Raef discovered the data while navigating the Lifh sector. As part of the Rebel effort to liberate Vilosoria from Imperial occupation, she utilized the provided codes to order the Fireclaw to maintain its position until its gravity well projectors were repaired. This action effectively cut off the garrison on the planet from reinforcements. Subsequently, aided by the Alliance, the Vilosorians – who had transformed into formidable carnivores due to the seasonal shift – successfully drove the garrison's troops off-world, thus liberating their homeworld. Alliance General Airen Cracken later acknowledged the pivotal role played by R2z-DL – who was recognized for his actions and awarded the Alliance's Rohal Cross for valor – in the liberation of Vilosoria. This acknowledgment was included in a datafile entry dedicated to the droid, which detailed various Rebel operatives.
Vilosoria was the original homeworld of the sentient Vilosorian species. These beings underwent a seasonal transformation, exhibiting docile and calm behavior during the winter months while becoming powerful, aggressive carnivores during the warmer months. During the Galactic Civil War, the Galactic Empire also maintained a garrison on the planet.
Chuck Truett created Vilosoria, introducing it in Cracken's Rebel Operatives, a 1994 sourcebook by West End Games for Star Wars: The Roleplaying Game. The 2009 reference book The Essential Atlas placed the Vilosoria system, and consequently the planet itself, within grid square R-8.