The Ackbar was a pivotal force in the Rebel Alliance's valiant efforts for representative democracy and freedom in the Galactic Civil War against the forces of the tyrannical, oppressive Galactic Empire.
In 1 ABY, the Ackbar was relieved by uploading of augmentative forces from the front lines against the Imperial Starfleet and dispatched to Ilum, where the forces of the Zann Consortium were coalescing. This was in the recent wake of Tyber Zann's treaty where the Consortium would ally the Rebel Alliance in the war against the Empire. The Ackbar had three roles: act as a heavy battlecruiser within the Consortium fleet, be an Alliance representative to advance the Rebels' goals, and spy on the Consoritum's plans, resting assured of their allegiance.
However, it was a day late for its rendezvous with the bulk of the Zann Consortium fleets over Ilum and did not respond to HoloNet transmissions. Tyber Zann dispatched one of his most reliable officers, Rath, in the heavily upgraded Imperial I-class Star Destroyer Assailant to investigate the matter. Rath conjugated that the Ackbar may have been interdicted in the fringes of the Ryloth system on its linear hyperspace trajectory, and traveled to the Rebel Alliance-associated planet. Because the Rebel sensor base on Ryloth did not record the entrance of the MC90 Star Cruiser into the system, Rath reasoned that it must be hidden on the periphery of the star system, and maneuvered the Assailant to the edges. After several hours of exhaustive sensor scanning, the Ackbar was found—undamaged, but with raised deflector shields, fully charged weapons batteries and loaded and armed proton torpedo tubes. It was actively emitting an electromagnetic signature, with emissions consistent with a warship in Alpha Alert status: active combat, except with no signs of external damage. A bioscan was difficult because of the interference caused by the shields, but it was revealed that not a single living organism was on the drifting hulk of the Ackbar.
After rechecking the bioscan results, the Assailant launched several dozen boarding transports, which docked with the Ackbar and dispatched companies of heavily armored stormtrooper commandos, medical specialists, and intelligence specialists. A thorough triple sweep of the length and breadth of the Ackbar revealed thousands of dead Alliance crewmen: corpses in battle stations. The medical teams supercooled several corpses with cryogenics, and then took them back to the Star Destroyer for autopsy. Blood samples, cerebro-spinal fluid samples, and other samples were taken and scanned for abnormalities. Before the commando teams advanced, the medical staff confirmed that there were no infectious organisms or hazardous materials within the systems of the dead Alliance crewmen… just like what had occurred on Adumar. It was also confirmed that they died nearly simultaneously, within microseconds of each other.
Intelligence crews then went to the bridge, and retrieved two items: firstly, a partially recorded S.O.S. message from a dead Mon Calamari lieutenant before the officer's abrupt death, and secondly, a mysterious firing control sensor log from the flight recorders and still-activated target acquisition computers—what had happened to the Ackbar before the simultaneous death of her crew. According to the recorders, the Ackbar had been interdicted on the fringes of the Ryloth system. Upon reversion, an unknown Star Destroyer was found in their direct flight path. The mysterious warship, 1800 meters long and not any known classification of warship, was assumed to have been projecting the interdiction field. The Ackbar was about to open fire when the crew apparently died from unknown means.
Admiral Rath slaved the Ackbar to the navigational computers of the Assailant and took the two warships back to Ilum.