The 2399 battle aboard the Artifact, a derelict Borg cube held by the Romulans, in which Seven of Nine reawakened its drones to drive out the Zhat Vash.
The Artifact was a disabled Borg cube that the Romulans had turned into a research site where former drones were freed from the Collective. Hugh, once a Borg drone himself, ran the program there. In 2399 Narissa of the Zhat Vash killed Hugh and began killing the former Borg aboard.
Seven of Nine linked herself to the cube through its central chamber and reactivated the dormant drones. With them she overwhelmed Narissa's forces and took control of the ship, then broke the link before the Collective could keep its hold on her.