The Nikardun conquests in the Unknown Regions were orchestrated by General Yiv of the Nikardun Destiny in an attempt to conquer various states of the Chaos. Yiv was successful in subjugating or otherwise making allies of several factions, but the involvement of the Chiss Ascendancy driven by Senior Captain Mitth'raw'nuruodo hindered and ultimately ruined Yiv's manipulations.
After a Nikardun attack on a refugee starship in Chiss territory, Captain Thrawn began to investigate the situation with the help of Admiral Ar'alani, discovering forces of the Nikardun Destiny in the Rapacc system. Throughout several encounters with Nikardun forces or their allies, Thrawn gained information about General Yiv and his regime, managing to outmaneuver the Nikardun in a battle near the Vak homeworld of Primea. Thrawn captured Yiv, who became a prisoner of the Chiss Ascendancy. Following Yiv's disappearance, no successor to Yiv was able to consolidate power and repair the damage Thrawn had done to their empire. As a result, the Nikardun conquests fell apart.
After interrogating the imprisoned Yiv, the Ascendancy learned the locations of remnants of Yiv's forces. Sufficiently convinced of the threat posed by these Nikardun remnants, the Syndicure allowed the Chiss Expansionary Defense Fleet to "bend" the protocols prohibiting pre-emptive strikes to hunt them down in the Nikardun campaigns. Two months after the battle over Primea, the Chiss were conducting the mission to the Vak Combine and believed they had nearly completed the Nikardun campaigns.
The Nikardun conquests provided the main plot of the 2020 novel Thrawn Ascendancy: Chaos Rising by Timothy Zahn. They also set the stage for the plot to destroy the Chiss Ascendancy, which served as the main plot of Chaos Risings 2021 sequel Thrawn Ascendancy: Greater Good. Greater Good revealed that the Grysk Hegemony agent Haplif instigated the Nikardun Destiny to conduct the attack at the edge of the Dioya system to distract the Chiss from discovering the civil war he had engineered on the planet "Sunrise."