The Mission to Celen was an Imperial operation to capture the Antarian Ranger Jilam Kester, who was charged with aiding refugee Jedi escape capture by the Empire, three weeks after the formation of the Galactic Empire. The mission was assigned to Squad 40 of the 501st Legion's Imperial Commando Special Unit, which was made up of Grand Army's clone commandos that had survived the Clone Wars.
After being briefed by Emperor's Hand Sa Cuis, Squad 40 was deployed to Chelpori, a city on the planet Celen, where Kester was spotted by the local security forces. Kester's hideout was monitored extensively by the local forces up until Squad 40 arrived. The squad was composed of RC-1309, nicknamed "Niner," and Darman Skirata, who were formerly from Omega Squad, as well as IC-4447, nicknamed "Ennen," and Bry, who were formerly of Galaar Squad. They stormed Jilam's hideout, where they expected to encounter minimal resistance. They were surprised when they came face to face with Jedi Master Iri Camas, the former Director of Special Forces and ultimately the commandos' old superior. Camas distracted the commandos, allowing Kester to escape, and ended his own life by igniting a gas line and causing the building to explode. Bry was killed in the explosion while the rest of the squad managed to escape.