The derelict on LV-178 was a crashed Dog-alien spacecraft discovered on LV-178 in 2159. The ship was buried deep underground but was uncovered when a trimonite mining operation run by the Kelland Mining Company broke through into the cave where it had come to rest. The miners were subsequently exposed to a Xenomorph outbreak as a result of the Eggs stored on board the ship.
Unlike the Engineer Juggernaut on LV-426, the architecture of the Dog-alien vessel was much sleeker and built using organic components. Rather than be built technologically, it is theorized by the miners on LV-178 that the vessel was grown through biological means. The ship was also significantly larger than a Juggernaut, so much that Ripley was awestruck by its scale.
In the time spent aboard the derelict, not much of it was fully explored by the miners. However, shortly after entering it for the first time, they came across what appeared to be a control center, and later on, a chamber housing Xenomorph Eggs that was theorized to have been a nursing area specified for breeding the organisms.
The origins of both the vessel and its creators is unclear, though it is obvious that the Dog-aliens held a great interest in Xenomorph XX121 and were using the ship as a nursing facility to breed the creatures. Based on the structural damage seen by the human miners, it is believed that the ship was struck by some sort of high-caliber weapon, most likely fired from another ship. Ellen Ripley believed that the Xenomorphs were let loose aboard the ship, prompting the Dog-aliens to fire upon it and cause it to crash on LV-178. After the crash, the planet's brutal and excessive sandstorms buried the ship deep beneath the surface, where it remained untouched for thousands of years.
The ship would eventually be discovered by human trimonite miners in 2159. The miners unwittingly awakened Xenomorphs laying dormant within the vessel, which slaughtered all of the miners stationed on the surface at the time of the ship's discovery. Soon after, a small team comprising surviving miners that had been stationed aboard the DSMO Marion in the planet's orbit ventured down into the mines themselves to recover fuel cells needed to escape from the system. They found the ship as well, but soon after were besieged by the Xenomorphs. The group set charges within the ship in an attempt to destroy it and prevent the Xenomorphs from spreading further off planet.