A significant contingent of Night Troopers loyally served Grand Admiral Mitth'raw'nuruodo, known as "Thrawn," during the admiral's time of banishment on the planet Peridea, situated within the distant galaxy.
Initially, the Night Troopers consisted of stormtroopers who found themselves aboard the Chimaera when Purrgil transported them away during the Battle of Lothal. Throughout the years of their isolation on the off-world planet Peridea, the military under the leadership of Grand Admiral Mitth'raw'nuruodo, or "Thrawn," experienced a reduction in personnel. Ultimately, Thrawn's stormtroopers, who rebranded themselves as Night Troopers, had their numbers dwindle to just one legion, which notably included a pair of death troopers. Thrawn appointed the fighter Enoch as the commander of this legion and formed an alliance with the three Great Mothers.
Via the Great Mothers, Thrawn communicated with his prior subordinate Morgan Elsbeth, who traveled to Peridea on the Eye of Sion with the purpose of extracting Thrawn, his troops, and the Dathomirian matriarchs. In accordance with his arrangement with the Great Mothers, Thrawn instructed his Night Troopers to commence the loading of his Star Destroyer with goods retrieved from their underground crypts. After the freed captive Sabine Wren departed to locate Ezra Bridger, Thrawn deployed two teams of Night Troopers with orders to eliminate both individuals.
However, the arrival of Ahsoka Tano resulted in significant losses for the squads, prompting Thrawn to order their retreat. Simultaneously, the cargo belonging to the Great Mothers was being transferred, and upon completion, the Night Troopers prepared to evacuate Peridea. Recognizing that the Jedi would attempt to impede their escape, a contingent of Night Troopers volunteered to remain behind to delay their progress. These volunteers were all killed, but the Great Mothers used their sorcery to revive them, transforming them into relentless undead warriors. Following the Chimaera's departure, the Great Mothers' Fortress was destroyed, eliminating the troopers who were still inside. Nevertheless, the majority of the legion successfully escaped with the Grand Admiral, with Ezra Bridger secretly concealing himself within their ranks, managing to escape after they arrived in the primary galaxy. The remaining Night Troopers were present on the Chimaera as they approached Dathomir.