Galleros Nul held the position of governor for Zelos II in 4 ABY and also served as the Mandated Commander of the People of Zelos following his declaration of martial law.
Within the Valley of Umbra on the planet, the Galactic Empire maintained a clandestine garrison. When New Republic agent Jai Raventhorn was apprehended by this base and subjected to interrogation, she managed to break free. She then captured the major in command, compelling them to contact Nul, thereby revealing the Empire's hidden operations. It is believed that Nul subsequently ordered an aerial attack on the garrison.
Following the revelation of the Imperial presence, Nul was persuaded to align himself with the newly formed New Republic.