This is a completely new scenario for Rome II, set in 311 A.D. Also available on Steam Workshop. The Tetrarchy of Diocletian Augustus divided the Empire in 293 A.D. Not long after, tensions arose between the various Emperors, all vying to become sole sovereign of the Roman world.
Based on "Constantine Rise of Christianity Patch 16.1".
The mod is mostly done. Roman factions have new unit rosters, some new buildings (mostly Constantine as Christian faction).
What I like is just those time persiod and established factions (many provinces under control). Mod still need some work with minor factions (unit icons etc).
But it plays smoothly and I like the battles (less arcade, more time to use tactics). Initial stage of war is scripted so from the start Romans have two wars. One is about who will rule west and the other who will rule east.
Constatine is Christian from the start, but it wasn's possible to make him change his religion (culture) in game (later). So he has bigger problems conquering Roman lands (other imperators share the same culture).
I hope the mod will be improving. But overall it's nice and playable.