Seoul 5 city was a derelict city located on the planet called Seoul 5. It represented the only known undamaged urban center belonging to the ancient Seoularians. Unlike other Seoularian ruins, which were heavily damaged from a possible comic conflict, this particular city remained remarkably preserved. Han Solo theorized its preservation might be attributed to a germ warfare strike that maintained the structural integrity of the buildings. At its heart, Onrai square featured a statue dedicated to the Mother Goddess named Onrai. Beneath the city's center was the crystal control room, which served as the city's power source, fueled by a cache of Seoularian crystals. The city's power, however, was deactivated when an Imperial scout extracted the Key crystal.
Prior to the commencement of the Galactic Civil War, an Imperial scout stumbled upon Seoul 5 and its city due to a Hyperspace mishap. Upon investigating the city, the scout discovered the crystal control room and its store of Seoularian crystals. Before his departure, he pilfered the vital key crystal, transporting it back to Imperial territory.
Following the Battle of Endor and the demise of the Emperor, Captain Drezzel arrived at Seoul 5, initiating an exploration of the well-preserved city. Utilizing two Xenoarchaeologists, namely Xathan and Fem Nu-Ar, the Imperials began the meticulous documentation of the city, with particular attention to the crystal control room. Simultaneously, the Imperial scout who had initially found the city forfeited both the key crystal and the coordinates of Seoul 5 to Han Solo during a card game. Solo, accompanied by his copilot Chewbacca, journeyed to the city, where they were immediately confronted by Drezzel and his adjutant Ssssk!. Solo managed to infiltrate the crystal control room, liberating Xathan and Fem Nu-Ar, who had been imprisoned by Drezzel for their opposition to weaponizing the Seoularian crystals.
During their subsequent escape aboard the Millennium Falcon, Solo forcefully inserted the key crystal into a control panel containing several other Seoularian crystals. This action triggered a massive surge of energy, threatening the destruction of the ancient city. Solo, along with the two xenoarchaeologists, returned to their ship and fled the planet. Despite Drezzel dispatching multiple TIE fighters in pursuit, the energy released by the crystals caused a catastrophic explosion, obliterating the city and the pursuing Imperial vessels. While the xenoarchaeologists mourned the loss of the knowledge that had been erased, they found solace in the fact that the Imperials would be unable to exploit the Seoularian technology for the creation of advanced weaponry.