B'Urgan was responsible for creating a device which prevented all Klingon and Federation weapons from working while allowing the invaders to use Breen disruptors. Worf had a specially modified Ferengi disruptor given to him by Nog which worked as well.
During the takeover, B'Urgan was able to contrust a communications device which allowed Rov to contact the Klingon High Council directly from the embassy. Eventually, Worf was able to regain control of the security system and flood the building with anesthizine gas knocking everyone unconcious. Along with all of the surviving members of Klahb except for Rov, B'Urgan was captured and held by the Klingon authorities. (TNG novel: A Time for War, A Time for Peace)