In 18 BBY, Jixtus, a Grysk operative who had formed an alliance with the Kilji Illumine nation, dispatched General Crofyp's task force to the Rapacc system in the Unknown Regions. Their mission: to seize a group of refugees who were in hiding on the planet Rapacc. This task force under the general's command consisted of Crofyp's Kilji war cruiser, the Anvil, and Colonel Tildnis's Kilji picket cruiser, named _Hammer_. They initiated an attack on Rapacc, engaging the Nikardun blockade frigate Aelos, which was under the commandeered control of the Paccosh. Crofyp demanded that the blockade frigate's captain, Uingali foar Marocsaa, stand aside and permit the Kiljis to capture the refugees. Marocsaa, however, refused, which led the general to prepare a crossfire assault on the Aelos.
The Anvil and the Hammer maneuvered to positions on the starboard and port sides of the frigate, respectively. Once they were in place, the Chiss heavy cruiser Springhawk arrived at the outer edge of the system. The heavy cruiser launched two plasma sphere weapons at Crofyp's flagship before entering the inner system to join the battle. Mitth'raw'nuruodo, a Chiss Senior Captain with the core name "Thrawn," ordered Crofyp to move away from the Aelos, which infuriated the general, who responded by firing spectrum laser volleys at the Springhawk. Shortly thereafter, the plasma spheres struck the Anvil's starboard side, and the war cruiser provided cover for the Hammer to allow the picket cruiser to escape. Thrawn permitted the Hammer to flee and then destroyed Crofyp's flagship using breacher missiles.
In 18 BBY, after discovering that a group of refugees he sought to capture had sought sanctuary on the planet Rapacc, Jixtus, the Grysk operative, deployed probes to the Rapacc system located within the Unknown Regions. However, the natives of the planet, known as the Paccosh, drove the probes away. Jixtus then tasked a task force from the Kilji Illumine nation, with whom the Grysk was allied, to travel to Rapacc. Their objective was to capture the refugees and transport them to a rendezvous point that would be determined by the commander of the task force, General Crofyp. The Grysk engaged the services of two Pahtfinder navigators: Qilori, who navigated Crofyp's Kilji war cruiser Anvil, and Sarsh, who navigated Colonel Tildnis's Kilji picket cruiser Hammer.
During the cruisers' voyage to the system, the Hammer reduced its speed, prompting Qilori to halt the Anvil so that the picket cruiser could catch up. Once Tildnis's flagship came into proximity of the war cruiser, the ships resumed their journey, reaching the inner Rapacc system simultaneously. There, they confronted the Nikardun blockade frigate Aelos, which was commandeered by the Paccosh and belonged to the Paccian Governance. The Aelos was in orbit around Rapacc. Crofyp issued an order to the Paccosh captain, Uingali foar Marocsaa, to move aside and allow his forces to seize the refugees. Marocsaa refused, leading Qilori to attempt a peaceful resolution by falsely claiming that the Paccosh, who he believed to be Nikardun, could prosper with the arrival of the Kiljis if they followed Jixtus's guidance. However, Crofyp revealed that the Pathfinder's claim was false and issued Marocsaa an ultimatum: either move aside or face death.
With the Paccosh commander's non-compliance, the general repositioned his warships to execute a crossfire attack on the blockade frigate. The Anvil moved to the starboard side of the frigate, while the Hammer mirrored this maneuver on the starship's port side. As the ships reached their designated positions, the heavy cruiser Springhawk of the Chiss Expansionary Defense Fleet arrived at the outer system. It launched two plasma sphere [weapons](/article/weapon], designed to disable vessels, at the starboard side of Crofyp's command ship. As the spheres approached their target, the Chiss executed a microjump and entered the inner system to join the conflict. Mitth'raw'nuruodo, a Senior Captain with the core name "Thrawn," ordered Crofyp to move clear of the Aelos, which he considered the Springhawk's prey, or face the "humiliation" of becoming collateral damage.
Crofyp, enraged by Thrawn's command, ordered his vessels to fire three spectrum laser at the Chiss vessel after the Kilji task force turned to face the Springhawk. While the Chiss and the Kiljis exchanged laser fire, the Aelos began to move, intending to attack the Illumine's forces. However, Thrawn, seeking to confuse the Kiljis and make them believe that the Paccosh were allies or at least neutral, fired a plasma sphere at the frigate to disable it. Marocsaa realized the reason for the Chiss attack and halted his attack after launching a shuttle, stopping the plasma sphere.
Shortly thereafter, the plasma spheres fired by the Chiss at the Anvil struck the war cruiser's starboard side, disabling the vessel's weaponry, sensors, and defenses on that side. On the cruiser's bridge, the Kilji crew attempted to reactivate their weapons, but their efforts were thwarted by the Chiss, who destroyed those weapons. As the Anvil moved to shield the Hammer to allow the picket cruiser to escape, Qilori attempted to flee in an escape pod. Crofyp declared that they would not escape and asserted that the followers of the Illumine's Kilji way of order and enlightenment religion stood, fought, and prevailed. However, the navigator called the general a fool and fled in an escape pod. Subsequently, several Chiss breacher missiles destroyed the Anvil, killing Crofyp, while Thrawn spared the Hammer, which fled.
The picket cruiser retreated to the "Sunrise" system in the Unknown Regions, where it maintained station with one of Jixtus's Grysk warships. Thrawn rescued Qilori, bringing his escape pod aboard the Springhawk, and tasked him with guiding the Aelos to the Hammer's location by using the Force to locate Pathfinder Sarsh. The pair joined the Paccosh aboard the Paccosh frigate, and Qilori guided it to Sunrise, where they boarded the picket cruiser and killed its crew before Jixtus's warship destroyed the Hammer and fled.
Shortly after the engagement, Qilori and the Aelos's crew traveled to the planet "Sunrise" in the Sunrise system, where Marocsaa informed Qilori that because the Pathfinder had participated in the attack on Rapacc, he was a prisoner of war. After Qilori departed Sunrise, he reported to Jixtus, informing him that the Chiss had destroyed the Anvil at Rapacc and that Thrawn and the Paccosh had boarded the Hammer at Sunrise.
The attack on Rapacc is depicted in the 2021 novel Thrawn Ascendancy: Lesser Evil, which is the final book in Timothy Zahn's Star Wars: The Ascendancy Trilogy.