The Czerka Corporation is a galaxy-spanning corporate arms dealer. Active since the early days of the Galactic Republic, they are known for their corrupt business practices, exploitation, and extermination of indigenous species on remote planets. In most conflicts involving the Sith and the Republic, Czerka has universally sided with the Sith, although on numerous occasions they have been known to weasel their way back into the Republic should the opportunity for profit present itself.
The Czerka Corporation is credited with the initial discovery of Kashyyyk, dubbing the planet G5-623, or Edean as it came to be known by stockholders. The company quickly embedded itself within the Wookiee tribal society, and started the Wookiee slave trade. The company would establish chieftains with the help of Czerka munitions and mercenaries, and in return the puppet leaders would provide Czerka with slaves. During this time, Czerka was also responsible for hunting many native Kashyyyk species to near extinction, such as the tach. Thanks to the actions of a reformed Revan, the chieftains were dethroned and Czerka was eventually driven off of the planet.
Czerka next set its sights on Telos IV, hoping to profit off of the reconstruction efforts after the planet was nearly destroyed during the Jedi Civil War. Czerka supplied workers and equipment in exchange for the rights to pillage the ruined planet of salvageable equipment. The company clashed with the Ithorian clan managing the restoration, and utilized its connections with the Exchange to commandeer several restoration zones on the planet. Thanks to the influence of the Jedi Exile during her visit to Telos IV, Czerka's operations were halted and their control over the restoration project was severed.
Czerka also had a substantial interest in the ore beneath Tatooine's sands. The company started many small mining installations on the planet's surface, Anchorhead being the most prominent. The company was dismayed to learn that the "valuable" Tatooine ore that it sought after was a mirage, corroding not long after it had been mined, making it useless for long-term construction projects. Czerka soon abandoned its mining operations, however Tatooine's harsh climate and remote location made it perfect for the company's secret weapons division. Several underground facilities were built for testing purposes, but for unknown reasons, Czerka simultaneously abandoned all of its operations on Tatooine.
Not much is known about the internal structure of Czerka, as they tend to be very secretive about their operations. The head of the organization is the President, and several corporate officers were seen in both Knights of the Old Republic games. Employees seem to have a very autonomous relationship with the company, for example Dern, a patrol officer, was allowed to poach tach within the Shadowlands of Kashyyyk, seemingly at the company's behest.
Czerka is not at all beneath allying itself with other shady organizations. The company has known ties to the Exchange, as well as the Sith, even alongside their dealings with the Republic. Czerka tends to go where the profit is, even without regard to the galaxy and its inhabitants. Perhaps one reason for their continued existence even beyond the Galactic Empire era is their willingness to set morality aside to turn a profit.
The Czerka Corporation served as an important antagonist faction in both Knights of the Old Republic games, and we know their products are still around during the Galactic Empire era thanks to Boba Fett's Czerka ZX Miniature Flame Projector. It is entirely probable that Czerka would align itself with the Sith once again during the Great War and provide many of the Sith army's weapons and equipment. It is also possible that much of the Bounty Hunter and Imperial Agent equipment may be Czerka branded.
Thanks to Tatooine's holonet page, we know Czerka was very active on the planet before the Great War, conducting secret experiments in underground bases. For unknown reasons, the company quickly abandoned their efforts and left their facilities unmanned. According to the HoloNet, the Sith Empire is well aware of Czerka's undertakings on Tatooine and is actively uncovering their secrets. Czerka also appears to have a foothold on Nal'hutta, seemingly poaching indigenous species as they did on Kashyyyk. The Bounty Hunter and Imperial Agent story lines involve a mission from Nem'ro the Hutt that requires them to kill a Czerka employee. Perhaps their animosity is an extension of the war between the Exchange and the Hutts on Nar Shaddaa.