In the 24th century of a parallel universe, Locutus' cube was a Borg cube whose crew kidnapped and assimilated Captain Jean-Luc Picard, who as "Locutus of Borg", led this ship against the Federation at Wolf 359.
Using Picard's knowledge of Starfleet tactics and weaknesses against them, the Borg inflicted staggering loses against the fleet in the Battle of Wolf 359, resulting in the loss of thousands of lives. During the battle, the Doctor's TARDIS made a brief trip to Locutus' cube. The Eleventh Doctor, accompanied by his companions, Amy Pond and Rory Williams, had travelled back from 2368 to acquire executive routines which would allow the Borg Collective to restore themselves and aid the Federation against their mutual enemy, the Cybermen.
After defeating the Starfleet task force, the Borg headed directly to Earth. Before its arrival, however, Data and Worf were able to retrieve Picard from the Borg cube and return him to the USS Enterprise-D as part of Commander William Riker's plan to turn the tables against the Borg. With the help of Captain Picard, Data was able to incapacitate the Borg cube and induce its self-destruction. (COMIC: Assimilation²)