An Imperial Refinery existed on the planet Kashyyyk, and it was there that the Galactic Empire manufactured a potent substance using the sap of the wroshyr tree. In the era when the Empire reigned, Saw Gerrera and his group of Partisans devised a scheme to enter the refinery with the goal of liberating the enslaved Wookiees. Cal Kestis, a Jedi Padawan who had traveled to Kashyyyk seeking out the chieftain Tarfful, met Gerrera and provided aid in the endeavor.