A dispute arose between the Galactic Empire and the Grysk Hegemony, situated in the Unknown Regions, after the Battle of Atollon. The catalyst was Emperor Palpatine's detection of a significant disturbance in the Force at the edge of the galaxy. Consequently, he dispatched his formidable agents: Darth Vader and Grand Admiral Thrawn. The military of the Chiss Ascendancy became involved when it was discovered that Grysk forces had penetrated Imperial territory.
The Imperial capital ship Chimaera journeyed to Batuu to investigate the cause and nature of a Force disturbance perceived by Emperor Palpatine. While the Chimaera was positioned above Batuu, Sensor officer Commander Hammerly identified four diminutive transports in a relaxed formation above the planet, which, combined with the six starships already present on Batuu's surface, totaled ten vessels. Commodore Karyn Faro communicated with Hammerly as the Chimaera's crew endeavored to gather as much data as possible on the vessels, inferring that they were either small freighters or small warships. As the data collection proceeded, two additional ships emerged from hyperspace directly ahead of the Chimaera at a distance of 400,000 kilometers. Hammerly concluded that these ships were, at minimum, a type of long-range heavy freighter, heading directly for Batuu. Faro surmised that all of the unidentified vessels were en route to Black Spire Outpost, where Grand Admiral Thrawn and Darth Vader were conducting investigations.
Hammerly determined that the two recently arrived starships had emerged from the same hyperlane as the Chimaera, approaching from over its aft. Shortly before a skirmish on Batuu involving Thrawn and Vader against a group of Darshi, one of the heavy freighters was advancing towards Thrawn and Vader's location, while the remaining vessels maintained their orbital position above Batuu. Vader instructed Commander Kimmund and his unit to intercept, scrutinize, and engage the other heavy freighter.
Shortly after the skirmish concluded, Kimmund and his stormtroopers approached the heavy freighter aboard the Darkhawk. However, the Grysk vessel detected the Darkhawk and altered its orbit to evade them. Defender Squadron One then arrived and successfully prevented the Grysk vessel's escape by disabling it, subsequently driving off the remaining smaller transports.
Kimmund managed to capture several Grysk warriors, whom Thrawn directed him to transport aboard the Chimaera for examination. Later, Kimmund and his legion were aboard the Darkhawk when a number of Grysk prisoners broke free and boarded the Darkhawk. Lacking communication and facing a shortage of troops, Kimmund anticipated certain death. Fortunately for Kimmund, Thrawn's Noghri assassin, Rukh, was present. Utilizing Rukh's cloaking device to gain an advantage, Kimmund and Rukh successfully subdued the retreating Grysks.
The Imperial–Grysk conflict functioned as the primary Imperial Era storyline for the 2018 novel titled Thrawn: Alliances, with half of the narrative unfolding near the conclusion of the Clone Wars. Elements of the conflict persisted into the novel's 2019 sequel, Thrawn: Treason.