The skirmish at Harrsk's fortress occurred during the Imperial Civil War.
High Admiral Treuten Teradoc dispatched his Crimson Command to embarrass Supreme Warlord Blitzer Harrsk. This occurred when Teradoc discovered that Admiral Daala planned to visit the world of his rival.
As Daala was being shown Harrsk's assembled fleet of Imperial-class Star Destroyers, the Crimson Command arrived in the system. They were led by Vice Admiral Gilad Pellaeon, and their mission was to eliminate Harrsk's flagship, the Shockwave.
Commander Kratas, Daala's subordinate, was inspecting the Shockwave and took control of the defense. Pellaeon's forces concentrated their fire on the capital ship, overwhelming its defenses and destroying it. While doing so, they damaged three other ships, but lost eleven of their own in the process.
Harrsk, in retaliation, compelled Admiral Daala to join his forces. Together, with the remaining eight star destroyers, they traveled to Teradoc's territory, but Daala prematurely halted the attack. This led to the events that culminated in the warlord meeting at Tsoss Beacon and the subsequent unification of the Imperial Remnant under Admiral Daala and Vice Admiral Pellaeon.
The Essential Atlas identified Kalist as Harrsk's capital world.