In planning out The Bastard's Blade, It seems to me that the fundamental aspect of the campaign is religion. Or rather, the influence religious belief has on the setting's peoples and how it motivates their behaviour. With that starting point, here are some unfocused thoughts on religion in Barael's Europe: 
- Christianity represents Law, civilisation, and order.
- Though historically significant, the specific differences between Arian and Trinitarian Christianity are likely to be glossed over in the campaign. I anticipate that efforts to distinguish the two as separate flavours of Law will be confusing (or, more accurately, that I won't do a good job of explaining the difference).
- That said, I can still represent the conflict between East and West: As the last man standing, the East Roman Empire sees itself as the "true" Christian authority, unspoilt (as it is) by the barbarian influence that toppled the West. Meanwhile, the Christian states in the West struggle to recover from Rome's fall, and some doctrinal details are bound to suffer for the greater good: You have to break a few eggs to make an omelet.
- Paganism represents Neutrality and teaches self-reliance for the benefit of the community.
- I'm thinking specifically of Germanic Paganism, and I'm applying a broad brush to include any non-Christian state.  In the interest of simplicity, I'll probably include about 6-10 deities, but without distinguishing between the Germanic, Norse, or Anglo-Saxon aspects of each.
- For now, I'm not touching Celtic Paganism. As the Celts begin converting to Christianity in the 5th century, I think it makes sense to depict Celtic culture as a mix of western Christians and Germanic pagans (via the Anglo-Saxons). I'm picking nits, but I think it's good enough for government work. If I want druids, I'll flaunt historical accuracy and make them cultists who worship demon lords.
- Who, by the way, represents Chaos and the rise of the individual to attain power over others. The roster includes Baal, Pazuzu, Dagon, Demogorgon, and perhaps a few others drawn from Babylonian, Mesopotamian, or Phoenician myth.
- Numerous cults venerate the demon lords (or aspects thereof); each focuses on different aspects—destruction, sadism, power, spider-worship, father-raping, essentially any value that promotes self at the expense of others. Or, perhaps more accurately, cultists are evil folks who worship demons to rationalise their depravity by associating it with a higher power.
- The demon lords are responsible for The Darkness, a pervasive evil force that covers all the white areas of the Shepherd Map. The Darkness spreads slowly west, subverting nature along the way. This is my rationale for monsters and arcane magic (and, by extension, non-clerical magic items).
- While all demon lords believe in spreading evil, they don't always agree on how to go about it. Thus, there are shifting demon alliances as they play politics and curry favour. Like, I'm sure Pazuzu would love to sink his talons into the Eastern Pope, but the other demon lords might have different mischief on their to-do lists, and struggles for priority amongst the demons occur as a result.
- All this brings up some spell-caster stuff: Christian clerics are Lawful, Pagan clerics are Neutral (and have access to reversible cleric spells). Demon lords have no clerics, but they are the source of arcane power, so all magic-users are Chaotic demon worshipers who pay for spells with their souls.
- In this light, I see Christian clerics from the west getting along with Germanic pagan clerics (after all, the pagan isn't a demon worshiper, and who knows—he might stand conversion?). At least they can probably work together in the same party. The same can't be said for clerics and magic-users—no cleric will be happy about hanging with a demon supplicant.
Listening To: The Police, Synchronicity
- Thanks to Evan for endorsing this format—turns out that it's pretty useful. Credit where credit is due.
- Emphasis on "state;" this excludes barbarian territories.