Kallo Enterprises was a business set up in the years prior to the Mandalorian Wars by Coruscanti businessman Reyus Kallo. The company dealt in electronics of all kinds, mostly communications and household appliances. With the onset of the conflict against the Mandalorian Neo-Crusaders, however, Kallo decided to expand into arms and armaments as well, becoming one of the Galactic Republic's chief military suppliers, along with companies such as Czerka Corporation. This partnership between Kallo Enterprises and the Republic continued into the Jedi Civil War, when Czerka defected to the Sith Empire.
Kallo Enterprises continued to operate until the end of the Light and Darkness War, the aftermath of which saw the Republic disband its army and navy. Kallo Enterprises had, by then, become so dependent on the sale of weapons and battle gear to the Republic that the disbanding of the military caused the company to collapse almost overnight. It was not, however, gone forever.
In 4 ABY Aryn Kallo, the eldest son of Reyus Kallo, was unfrozen from carbonite after almost four millennia by the Nightsister Silri. After killing Silri and leaving the planet, Kallo annointed himself as a Dark Lord of the Sith and gave himself the title of Darth Nathemus. Needing a disguise for the public eye, however, Nathemus kept his birth name and restarted Kallo Enterprises. Masquerading as a businessman, Nathemus was able to integrate himself into a galaxy that had changed much since his incarceration, and he kept the disguise up, and Kallo Enterprises working, until he launched his own war against the galaxy decades later.