A bureaucratic organization attached to the Fifth Legion by order of the Consul and Legate of the West March, the Administratum handles a number of functions to help the legion achieve its goals: the keeping of records, maintenance of weapons and armor, balancing of legion coffers, tracking of Auxilia members, and the naturalization of new citizens. 

Its membership is composed of the following subdivisions: the Castellan and Princeps, Masters, Sergeants at Arms, and Freelancers. The Castellan is the overall leader of the Administratum, and oversees all of its functions. The Princeps serves as their adjutant, assisting them in their duties and serving as their replacement should they be killed or incapacitated. Masters are the specialized figures under the Administratum's authority, charged with one of its tasks and granted overall authority over its execution. The Masters of the Administratum are the Master of Records, Master of Armaments, Master of Coin, Master of the Auxilia, and Master of Cives. Sergeants at Arms protect the members of the Administratum as they carry out their duties, working as contracted mercenaries as opposed to dedicated legion members. Freelancers are are a second type of contracted mercenary, serving in non-combat roles. They deliver messages or assist with other tasks.