Imperium

This is a limited “resource” that determines two factors, the number of armies, navies and agents you can field at once, and the number of Edicts you can issue to individual provinces that you completely control. Imperium is gained simply by conquest and constitutes an ordinal scale rather than numeric value. Reaching the next level on the scale, as shown in the Overview tab of the Faction window, provides an increment in this number of units and Edicts.

Edicts are very relevant to province management. To set an Edict if you have one spare, choose one on the leftmost tab on the Province Overview window while a settlement in the province is selected. The Edict provides a province-wide benefit. Most useful I think are Bread and Games for improving province level public order, and Tax Harvesting for improving province wealth. Note that when changing Edict from one to another or between provinces there is a one turn delay before it takes effect.

With Imperium, the virtuous circle of resource management is complete. All those interconnected resources are in the end used for empire building, and this empire building in return directly boosts the other resources through an increased number of available Edicts.