Setting Overview and Ground Rules

If you happen to be in an elevator with me and ask, "What's this Bastard's Blade campaign about?" you'd get a reply something like this:

The Roman Empire that once dominated the civilised world has been reduced to a fraction of its former glory, and the barbarian warlords who pushed it back are the new masters of Europe. They have reawakened the old gods Christianity put to sleep, but in so doing, let loose powers they had forgotten how to control. Europe is a chaotic realm of warriors, sorcerers, and thief-kings, all vying for power and wealth in the vacuum of Roman stability. Will the PCs seek fortune as mercenaries in the service of a barbarian warlord? Or perhaps they’ll win a name by recovering the treasures of ruined Christian halls. Maybe still they’ll stem the tide of Chaos and revive the worship of the One God to bring order to an unruly land.

There's a lot potential there, so I'm going to lay down some ground rules to keep me on the beam:

The Map is Canon
I'll describe and populate the map based on what the map shows, so where there's a question about borders, cities, natural features, etc., the map is considered authoritative.

History Optional
I will neither achieve nor strive for 100% historical accuracy. This means I will misinterpret stuff, ignore important details, and reinvent in directions that real-life historical figures and events did not go. My goal is to create a setting based on history, not to follow the track of real world history in my setting.

Religious Freedom
At the time depicted by the map, Christendom consisted of Arian states, the Roman Catholic church, and Eastern Orthodoxy. Judaism exists in the Middle East, Zoroastrianism to some extent in the Persian Empire, and other various pagan states throughout Africa, and the Eastern lands. I'm bound to oversimplify the religious landscape to suit the campaign, but I do so only as an expedient to play and not, by any means, as a commentary on any religion or statement of faith. Feel free to send me a gentle reminder if you feel I've crossed this line.

Fantasy Stuff
I'll translate the S&W rules to what I hope to be intuitive historical analogues. Again, there's a lot of room for interpretation (e.g., what's does "magic-user" mean in fantasy Europe of 486?), but I'll explain myself where the need arises, and ask you to bear with me ('cause it won't all make sense).

Pick and Choose
There's every chance that I'll inject bits and pieces of historical "what-if" into the mix. It may not be practical, and it probably won't be the logical outcome of historical precedent. But, this is about making an exciting setting, so there's going to be a few mystery cults, some undead pontiffs, magical weapons like Excalibur, "real-life" golems and djinn, and white dragons on the Asian steppe. I'll try to weave them into the setting logically, but given that this is magic and the real world isn't, you'll need to suspend your disbelief here and there.

Next up, a short list of source material.
Listening to: Antibalas, Who Is This America?