Foundry Four was a hidden base, factory and repair yard on the planet Xorrn. The base was a former Separatist droid foundry. It was hidden between the wreckages of Trade Federation Core ships, that got destroyed during the Bombardment of Xorrn at the end of the Clone Wars.
The Geonosians tried to build their traditional hive spires to house Droid foundries on Xorrn. However the thin crust of planet caused hive spires to collapse before any droid could be produced. To counter this, the Geonosians started to excavate the hives instead of erecting them. Just like other foundries, Foundry Four was dug into surface of Xorrn. Before and during the Clone Wars, Foundry Four was a functioning warren of five separate underground factories joined by a central command center. Each factory had two landing shafts for the supply of raw materials and to move out finished products. Futhermore they functioned as exhaust vents for factory waste. The shafts had a depth of four hunderd meters, with a corvette-sized landing platform. The landing pads were equipped with four tractor beam emitters to assist landing. Only two landing pads remained in service when Clan Assembly controlled the Foundry. The Control Center was located above a large magma chamber. Previously used as a monitoring station, Clan Assembly used it for meetings.
The Geonosians used Xorrn to illegally produce Battle droids hidden from the Galactic Republic. Factories like Foundry Four managed to turn out millions of battle droids. Just after the outbreak of the Clone Wars, the Republic discovered the facilities on Xorrn. Turning the planet of Xorrn into a warzone. After various failed attempts, the Republic didn't want to waste anymore resources on capturing the planet. A sector fleet bombarded Xorrn from orbit, destroying dozens of Core ships in the process. The bombardment significantly damaged Foundry Four. All but two of its landing shafts collapsed.
After the Clone Wars, Separatist refugees from Gall under Jans Coorsa moved to Foundry Four. They reopend Foundry Four and started to produce replacement parts and starship armaments on order for the Rebel Alliance, pirates and Mercenaries. During the Galactic Civil War, it was the site of a large-scale battle.
- Friends Like These (First appearance)