Kubus Oak was a Bajoran. During the Occupation of Bajor, Secretary Kubus served as the special liaison between the Bajoran Occupational Government and the Cardassian Union. His duties included signing off on Cardassian orders for new Bajoran mine laborers. Though the orders were effectively death sentences, Kubus never once refused to authorize them. He rationalized his actions with the belief that the Occupation would have been far worse without him and others in the Occupational Government.
When the Occupation ended in 2369, Kubus left with the Cardassians and retired on Cardassia Prime. In absentia, he and other Bajoran collaborators were exiled from Bajor by the Ilvian Proclamation, on which Kubus's name was listed fourth.
In 2370, Kubus arrived at Deep Space 9, hoping to spend his remaining days on Bajor. He was quickly recognized and arrested by Chief of Security Odo. After Major Kira Nerys denied his request to return to Bajor, he contacted Vedek Winn Adami and gave her circumstantial evidence that Vedek Bareil Antos, not Prylar Bek, was the traitor responsible for the Kendra Valley Massacre. Wanting to use the information against Bareil in the upcoming election for kai, Winn granted Kubus sanctuary on Bajor. (DS9: "The Collaborator")