It probably was part of some island/small continent civilization in the Pacific. It's referenced in countless other civilizations across the globe, and who knows where they were centered exactly. These kind of "superhumans" that lived there likely migrated to places like the isle of Sardinia (and then to the Levant and other areas) and possibly the tip of Scandinavia (which was later submerged) as well as places like Okinawa .
It almost certainly was a monotheistic religion based around a snake of some kind, and at any rate that's why we have a never-ending collapse of "civilizations" and insistence that their must be bad and evil because they've all been borrowing the concepts to suit particular relativistic needs, not because no one ever agreed to live differently. Even Bioware, despite it's progressive leanings also leans on concepts of "fallibility" in minute but nonetheless noticeable ways.
Anyway that's a portrait emerging from a whole bunch of people studying the situation, one of the earliest to focus on these theories and patterns was James Churchward although he also had this unfortunate racial ideology angle to it. Others like Graham Hancock have been picked up on the same things.
That religion didn't have like a "hell" for instance, just the earth plain, natural disasters being the biggest enemy, it's likely that in the aftermath of many chaotic events, floods, volcanos, people were interpreting figures from religion or mythology
I doubt any morality could encompass the entirety of humanity, all and forever, but uniting all the most prosperious independent nations, and even many of the less prosperous? Sure.
Kant, Hegel, Descartes, Nietzsche, Aristotle, Rawls, Rand, Martin Luther King, Gahndi, every single one is borrowing from much older concepts.
Anyway, Bioware is cool and all but I'm left wanting more... more sharp divisions, more clear moralities, more heroism, whatever,j ust more.