Serroco, the homeworld of the Stereb species, was a planet in the Ploo sector of the Expansion Region. A muddy world, Serroco was constantly buffeted by ferocious storms and tornadoes that often forced the Stereb to retreat to underground shelters and catacombs. The world was dotted by the grand stone Stereb cities and newer settlements populated by Humans from the Galactic Republic. Serroco was a full member of the Republic, and when the galactic government went to war with the Mandalorian warrior clans in 3963 BBY, the planet became a flashpoint in the growing conflict.
Admiral Saul Karath, anticipating a Mandalorian advance on the planet, rounded up a sizable battle group to defend Serroco and placed camps among the Stereb cities. Disdainful of the location of the camps and seeing it as a dishonorable approach, the Mandalorians nuclear-bombed the planet directly when their force arrived at Serroco, destroying the cities entirely. One Republic Navy pilot, Carth Onasi, saved many Stereb lives by calling down false tornado warnings and sending them to their underground shelters, which shielded them from the blasts. Life on Serroco continued on despite the devastation of the planet, and a Republic military presence was reestablished there by the time of the Galactic War several centuries later. By the Imperial Period, a small population of Stereb continued to exist on Serroco.
Serroco was a muddy, rainy world located in the Serroco system of the Expansion Region's Ploo sector. The homeworld of the Stereb species, Serroco had an atmosphere that supported other sentient life forms, such as Humans. Expansive dirt fields could be found on the planet, with patches of trees and other plants. It rained frequently on Serroco, and bigger storms often broke out, with tornadoes sometimes posing a threat to the Stereb.
The planet had multiple continents and revolved around at least one star. Serroco's land appeared green from space, with oceans covering a large part of the planet's surface. The Mandalorian nuclear attack on Serroco during the Mandalorian Wars between the Galactic Republic and the Mandalorian warrior clans had a great impact on the planet's landscape—the world's Stereb cities were destroyed, leaving only glass craters.
By the time of the Mandalorian Wars, Serroco was a full member of the Galactic Republic, and Human settlers from the Republic had put down roots on one of Serroco's nicer continents. The Republic Navy maintained an orbital watchstation above the stormy planet, issuing tornado warnings to the Stereb, who were not adept with the technology themselves. However, some personnel stationed at the watchstation found it to be a boring posting and amused themselves by calling in fake tornado warnings during festivals, sporting events, and other gatherings, a practice that ended when Serroco's senator complained. Multiple Jedi were also regularly assigned to the planet—during the Mandalorian Wars, one of the Jedi on Serroco was the Human Meetra Surik. In 3963 BBY, the Mandalorian warrior clans advanced on Serroco from the planet Jebble—anticipating an attack, Admiral Saul Karath assembled Battle Group Serroco and set up a staging area on the planet, with encampments among the Stereb cities. The camps were home to a great number of Republic Navy personnel, in addition to fringers selling food and other services to the soldiers. Camp Three featured the extremely popular Little Bivoli mess ship, which was run by two fugitives: Zayne Carrick, a former Jedi Padawan wanted for the murders of his entire class on Taris, and Marn Hierogryph, a petty criminal believed to be his accomplice. Despite being two of the most wanted beings in the Republic, Carrick and Hierogryph were able to evade notice right under the nose of the Karath and his battle group.
Karath and his team thought they were completely ready for the Mandalorians—they figured that the Mandalorians would not dare to attack the Stereb cities directly, for fear of wrecking potential loot. Karath set up a massive cordon of ships surrounding the planet, hoping to stop the Mandalorians dead in their tracks. On the planet below, however, Carrick had a Force vision of the Mandalorians destroying the Stereb cities and annihilating the Republic camps, and he decided that he immediately needed to warn Karath. In a rush, Carrick stowed away on hotshot Republic pilot Carth Onasi's ship, the Deadweight, convincing Onasi of his seriousness and hitching a ride with him to Karath's bridge on the warship Courageous. There, Carrick was recognized as the so-called "Jedi killer" and accused of being a Mandalorian spy. His warnings went unheeded. Soon, a Mandalorian force came out of hyperspace at the edge of the system. Disgusted by the Republic's "dishonorable" tactic of placing its camps so close to the Stereb cities, the invaders started off the proceedings by firing off nuclear missiles—to Karath's surprise, the missiles angled around the Republic ships, heading toward the Serroco camps. As Karath did not expect this to happen, the camps' missile defense systems were not online, and the planet was left defenseless.
Impacts were counted near twenty-seven populated areas. While the Human settlements sustained heavy damage, the Stereb cities were simply gone, turned into glass craters. Furthermore, only eight of the Republic ships on the surface escaped destruction, one of which carried the Jedi Knight Meetra Surik. Before the missiles were launched, Onasi had buzzed down tornado warnings to seventeen Stereb cities, hoping that their underground catacombs could protect them if Carrick's vision came true, an endeavor that saved many lives. Serroco was nearly annihilated, its surface covered in massive craters where once had been cities and settlements. The Republic immediately condemned the destruction of Serroco as a tragedy and a horrific crime, and the devastation was not soon forgotten. Republic propagandist "Benegryph Goodvalor" chose Serroco as the name of his imaginary warship in transmissions aimed at the Mandalorians, and the planet became the namesake of a real Republic ship by the time of the later Galactic War. "Goodvalor" was actually Marn Hierogryph, who, along with talented Trandoshan cook Slyssk, had narrowly escaped Serroco's destruction on a stolen troop transport, inadvertently saving half of a sleeping battalion. The Republic Defense Ministry turned the rescue into a propaganda story, with "Goodvalor" being feted as the "Hero of Serroco".
Life on Serroco still continued, and by the time of the Jedi Civil War several decades after the Mandalorian conflict, Serroco had a leader named Lelin-Dor, who was known as the First Patriarch. During the war, Revan, the Dark Lord of the Sith, had Lelin-Dor assassinated, believing him to be a destabilizing influence. By the time of the Cold War a few centuries later, a Republic military presence had been reestablished on Serroco. In that same time period, archaeologists discovered an intact Stereb shelter left over from the Battle of Serroco, containing many previously-lost Stereb artifacts. During the Imperial Period, thousands of years after the Battle of Serroco, there was still a small enclave of Stereb on the planet.