You bring up an excellent point about Better Angels, and it is especially important considering how the mechanics demand a moral judgement for even the most minute physical actions.
In the GM chapter of the book, there is a list of options Stolze provides to the GM about what, exactly, the super-powered demons are. One is that they are quite literally biblical demons from Judeo-Christian faith, but there are many others provided. He suggests they might be psychic manifestations of the collective unconscious (supervillians are Evil, and the combined psychic force of the perception of evil CREATES a demon). They might be Lovecraftian horrors or gray-liens disguising themselves as demons.
All of this is further complicated by the GM's building of the setting. There is no "canon" history as to how long super-people have been around, be it millinia or since Tuesday.
I struggled with how I was going to handle this, and I eventually decided on "Gonzosity," which is Greg's option for everything at once. I've interpreted it as "nothing at once." Demons, whether real or archetypal concept, are supposed to be liars, so I'm going to let the players describe their origins however they wish. I'm house-ruling that a Faustian pact can buy you definitive knowledge about the setting and plot from the demon's perspective (e.g. the GM tells you), but beyond that, demons can say they hail from any faith, planet, culture, or whatever.
If a definitive system of morality for the entire world gets revealed in the campaign, it will only be at the behest and design of the players. I'm uncomfortable inflicting a moralistic worldview of absolute certainty on everyone. While I briefly worried that would keep from running the game, I quickly realized that it could actually be its greatest strength. Despite having more evidence than those around them, players can still be uncertain about the moral laws of right and wrong, yet they are being judged (mechanically on their character sheets) in such a way the implies such a rigid code of ethics must exist. At least initially, I want the player to feel as if they are on trial in a foreign court with contradictory and unknowable laws.
The moral quandary then becomes do they take the burden of such a trial on themselves, trying to do what they can with it and saving someone else the pain? Or do they do the other "right" thing, which is resist temptation for the sake of their soul/essence/salvation/etc, thus passing the responsibility onto someone else?
