Attacker Four was a heavy cruiser class vessel used by the military forces of the Chiss Ascendancy. This heavy cruiser, as part of a group of four, was dispatched to attack the Chiss warship known as the Vigilant. These orders came from the Nikardun Destiny faction of the Lioaoin Regime. The attack occurred when the Vigilant was attempting to extract Senior Captain Mitth'raw'nuruodo from Primea, the homeworld of the Vak. Aboard a commandeered Vak patrol boat, Thrawn opened fire on Attacker Four. This action inflicted considerable harm while the Lioaoi forces were disoriented by the unexpected assault from a Vak starship, despite the Vak being neutral. Using Attacker Four as cover, the Vigilant successfully evaded the other cruisers and escaped.