The operation known as the Mission to Celen was conducted by the Galactic Empire during the period of the Great Jedi Purge. Its objective was the capture of Jilam Kester, an Antarian Ranger accused of aiding Jedi refugees in evading Imperial capture. This took place a mere three weeks following the Empire's establishment. Squad 40, a unit within the Imperial Commando Special Unit of the 501st Legion, was assigned to this mission. This squad comprised clone commandos from the Grand Army of the Republic who had survived the Clone Wars.
Sa Cuis, an Emperor's Hand, briefed Squad 40 before their deployment to Chelpori, a city located on the planet Celen. Local security forces had identified Kester in Chelpori and maintained extensive surveillance on Kester's hideout until Squad 40's arrival. The squad consisted of "Niner," designated RC-1309, and Darman Skirata, both formerly of Omega Squad, along with "Ennen," designated IC-4447, and Bry, previously members of Galaar Squad. Upon storming Jilam's hideout, anticipating light resistance, they were surprised to encounter Jedi Master Iri Camas, the former Director of Special Forces and the commandos' former commanding officer. Camas created a diversion, enabling Kester to escape, and then took his own life by igniting a gas line, causing an explosion that killed Bry. The remaining members of the squad managed to escape the blast.