Scope
The motivation behind building Cumae: The Orbis
A high fantasy D&D (1e, 2e, 3e, 3.5e, and 5e) setting that merges Gene Wolfe (Books of the New Sun) with some of Michael Moorcock (Gloriana) and then recasts it all through the lens of Byzantium, if Byzantium were more Gnostic than Greek orthodox.
Why is the Orbis?
It exists as a way to add moral ambiguity and deep character exploration on top of the normal pillars of combat, exploration and social interaction. It presents the basic theme that every 'bad guy' considers himself or herself a good guy, and that characters need to choose their allies, and their enemies, carefully. It also gives space to develop long-term plotlines that are player driven, inside an inherently existential world - Shroedinger's NPC is a very real phenomenon. Who is behind the door? Whoever needs to be, not necessarily who a premade, boxed-set guide says is there.
The goal of the project
Mostly the gratification that comes from a dynamic, living world not bound by official minutiae and that players can experience deeply every week, not in boring lore dumps but in interesting interactions with the world and those in it, for good or ill.
Cumae: The Orbis's Unique Selling point
The Orbis rejects the standard Tolkeinesque, Western European version of fantasy in favor of the fascinating East, from the Balkans to Persia, India, China and Japan, as well as the precolombian Americas. One nation, Minon, is sort of a French/Western Europe analog but in its current iteration it draws much more from places like Wallachia, Sarmatia and Parthia than from the west.
This is not merely intended to 'change things up' but to highlight the fact that according to Google, Medieval Europe means Western Europe, and the study of even mundane parts of the history of Hungary, Romania or Slavic countries seems hopelessly obscure. Considering the awesome treasure trove of incredible folklore, exciting battles and fascinating royalty, the rest of the world is missing out by this myopic interpretation. The fact is, if you want fantasy, it's more fantastic when grounded in the east rather than the west.
Theme
Genre
High Fantasy, D&D 5e compatible.
Reader Experience
While the game certainly has plenty of combat, exploration and roleplay, much of the truly interesting conflict and challenge is player-generated as a natural result of being presented with a great deal of moral ambiguity, and with few pre-decided outcomes. A minor character from a random encounter might rise up to become a great goddess, while the 'obvious' bad guy might meet his end rather easily. Factions and alliances are paramount, between groups and individuals. Character advancement isn't merely on the sheet, but owning and maintaining lands, and the acquisition and protection of wealth, trade routes and tax money can all play a part. The tone is generally light, but circumstances can lead to some very dark scenarios, especially if players don't push back against some of the more morally questionable peers and rulers they will encounter.
Reader Tone
The world is dark from the Gene Wolfe influences, and an emphasis on massive, unknowable ancient gods and dark fallen empires, but brightened by some of the more absurdist elements of Michael Moorcock's Gloriana as well as, where possible, real Eastern European folkloric characters, monsters and stories. The trick is to keep it more game of thrones and less monty python and the holy grail.
Character Agency
The world is inherently existential with very little set narrative. There are factions and NPCs with goals, often in conflict with those of the players, though just as often in parallel or aligned to their interests. Players can go anywhere and do anything they are capable of doing. They can buy and sell, they can fall in love and marry and have children, they can worship angels or demons, destroy cults or join them, fight or talk or flee. There are no real rails; prep is dictated mostly on where they seem most likely to go, and who will be there, and what they want - ideally, what they want that they can't have if the characters also get their way, to create deeper conflict and genuine interest. This puts a lot on the DM to be flexible and spontaneous to keep it from getting boring or repetitive, and to ensure the players realize the choice really is theirs.