The Imperial Reforms trigger when the Romans are unified under the Roman Empire faction (which happens when only 1 roman faction is left alive).

The Marian Reforms become obsolete (but the Auxiliary System remains).

The Marian Legionary Cohorts units are replaced with Imperial Legionary Cohorts. Imperial Legions (composed of 1 Legionary First Cohort and 9 Legionary Cohorts) become available for recruitment in cities with the Roman Polity and Army Barracks buildings, at the cost of 3.000 population and 10.000 denarii.

Roman generals switch their bodyguard from the Proconsul's Bodyguard to the General's Armoured Bodyguard.

Additionally, certain other units become available:

• 8 Praetorian Cohorts spawn in Rome. They are not retrainable, but replenish 15 - 22.5% each turn they end in Rome.
• Cataphracts and Cataphract Archers become available in Antioch. There can only be a maximum of 8 of these units at any time.
• Sarmatian Auxilia become available in Chersonesos. There can only be a maximum of 6 of these units at any time.