Transport 904 functioned as a ship within the transport fleet of the Galactic Empire. In approximately 18 BBY, its assignment was to reach the planet Wayland and the recently constructed facilities located there. However, the cloned Zillo Beast it was transporting escaped containment, causing significant damage to the vessel. Consequently, the badly damaged transport was forced out of hyperspace and ultimately crashed on Silla. Ciddarin Scaleback, an information broker, learned of the ship's predicament and dispatched Clone Force 99 to salvage any valuable items, completely unaware of the true nature of its cargo.
The mission assigned to Transport 904 involved the delivery of a cloned Zillo Beast to an Imperial cloning facility situated on Mount Tantiss on the planet Wayland. Due to the covert nature of the Imperial cloning program, the ship's intended course was kept secret from the bridge. The hull lacked any identifying marks to maintain organizational secrecy.
Around the time of 18 BBY, Transport 904 was en route to Wayland when the cloned, juvenile Zillo Beast it carried managed to break free from its confinement. It then proceeded to assault the ship's crew. The creature consumed nearly all of the crew and inflicted such severe damage that the ship was violently ejected from hyperspace. The Zillo Beast then pursued a surviving Imperial clone commando through the ship's corridors. As the commando braced himself with an electrostaff to confront the creature, the beast surprised him, dragging him into the ceiling shafts with a scream, where he met his end and was devoured. Eventually, the ship suffered a catastrophic crash on Silla.
Shortly thereafter, the renegade clones comprising Clone Force 99 received information from their contact, information broker Ciddarin Scaleback, regarding the downed ship. They were instructed to retrieve any valuable cargo it might contain. Upon locating and boarding the vessel, they soon encountered the cloned Zillo Beast following their exploration, resulting in an immediate attack. The team successfully drove the beast into the nearby forest by detonating a grenade, creating an escape route for the creature through a hole in the ship's hull. While Hunter and Wrecker gave chase to the Zillo Beast aboard the Marauder, Tech and Omega returned to the remains of Transport 904, attempting to access its database for information. Their efforts were cut short when Imperial V-wing starfighters, dispatched in response to the crash, arrived and destroyed the transport to conceal its purpose.