A Hammerhead-class cruiser saw active service during the era of the Old Republic. Millennia later, its ruined remains were discovered on the planet Mustafar.
Sometime during or following the Galactic War, which took place in the Old Republic period, the cruiser met its end, crashing onto the volcanic landscape of Mustafar. The planet's intense volcanic activity and constantly shifting terrain resulted in the wreckage being entombed beneath layers of lava, rock, and volcanic ash.
After thousands of years had passed, a massive seismic event unearthed the cruiser's remains. This occurred during the Clone Wars, when the Confederacy of Independent Systems held dominion over the planet. Upon discovering the wreck, Neimoidians from the Separatist faction immediately began a thorough investigation. They zealously guarded the crash site, preventing any Mustafarian individuals from accessing the wreckage. No records explaining the crash could be found on board, and no engineer who examined the vessel could determine the cause of the accident. Within the wreckage, the Neimoidians came across the deactivated form of a very ancient assassin droid. When they brought the droid back online, it went berserk, causing the deaths of several Neimoidians and the battle droids assigned to protect them. The droid was identified as HK-47, a notorious assassin droid who had previously served the Jedi Knights Revan and Meetra Surik many millennia prior. Separatist experts were astounded by the advanced technology used in the droid's construction, but they were unable to erase its memory due to its incredibly complex thought matrix. To overcome this, the engineers transferred HK-47's memory and thought patterns into a functional subsystem of the crashed cruiser, taking the empty chassis with them. While Separatist scientists analyzed HK-47's body at their new droid factory, the droid's AI was able to integrate itself with the ship and seize control of its operational systems, which forced the scientists to seal off the ship and sever its uplink. The cruiser was then abandoned, leaving behind valuable salvage.
During the time of the Galactic Civil War, a group of Salvage bandits established a presence at the site, hoping to claim any valuable technology for themselves. They were determined to keep others away from their potential treasure. Twenty years after the Separatists were defeated, in 1 ABY, a group of spacers employed by Mensix Corp explored the wreck of the Hammerhead-class cruiser, seeking to recover power rods and other valuable technology. HK-47 used the ship's systems to communicate with and deceive the spacers. HK-47 directed the spacers to assist in transferring his artificial intelligence from the ship to a nearby abandoned research facility, and then to an old Separatist droid factory on Mustafar. This ultimately allowed HK-47 to be reunited with his physical body and to commence the creation of a vast droid army.
The destroyed Hammerhead-class cruiser made an appearance in the 2003 video game Star Wars Galaxies, which was a massively multiplayer online roleplaying game that was created by Sony Online Entertainment and distributed by LucasArts, before it was shut down on December 15, 2011. The Hammerhead cruiser wreck was incorporated into the game when the Trials of Obi-Wan expansion pack was released on November 1, 2005. The ship was located on the central island, near the Central volcano, and was guarded by numerous Salvage bandits. It played a role in a quest that involved the assassin droid HK-47. During this quest, the player would enter the ship and use its computers to communicate with HK-47 and facilitate his transfer to the droid factory, where he would eventually be restored to his body.