$35414! Rival old ones are now officially a thing! Woo!
KingDinosaurGames - Can you give some examples on the engine changes you'd like to make for the next stretch goal and how they'll affect gameplay? Feel free to get very technical.
The game was designed with two phases, an open-ended beginning where you, as the Old One, spread your minions forth into the world to begin to sow chaos and begin to set your plots in motion, and the second part is the world's realization that you have returned and their attempt to respond to that while being plagued by all the scheming and evils that you set loose in the first part. We wanted the game to have a narrative, strategic drift that you struggle against, either by trying to keep awareness down or by crushing the most threatening elements of the world. However, no matter what you do the Chosen One will emerge, the Alliance will form, and the world moves towards a climactic final struggle - though if you've done a good job the form these elements take will be greatly crippled. In addition to this, each game is self-contained, there is no cyclical element that we had originally envisioned - when the game ends it is over and you can start a new one (with one exception, we do currently track corrupted heroes for one Old One's special ability).
We will be removing these dependencies in the logic of the engine and gameplay balance, essentially reducing the imperatives of the second stage of the game and making the entire process conditional on other elements of the world. The Chosen One is no longer a foregone conclusion, instead Prophecies can be randomized and based on their completion the fates will spawn events and champions accordingly - and instead of his death leading to a new Chosen One instead the world will mourn, and seek another prophecy. The Alliance AI will become much more versatile, instead of being a group of Nations that are pulled to a final confrontation with you there may be several competing Alliance AIs, some of which will pursue the traditional path of alliances and conquest to seal you away others to whom survival is their only goal. Crushing an Alliance does not spell the end of the world, much like the modified defeat of the Chosen One it is just another significant event.
We are modifying the way Sages research and discover the Old One, removing the "bonus over time" that comes from the amount of your Ancient Power and increasing the bonuses and penalties that can be gained by actions throughout the world. We're adding additional methods of controlling your rise, adding or removing Ancient Power based on what you've done and also pivoting around controlling certain areas. Together with these and other changes you are better able to manage the level of impact you have on the world, and the world will react accordingly - maintaining its more open-ended simulation status instead of moving into a more aggressive period.
We're modifying the way heroes spawn, allowing you to customize the rate at which they are created and to set it over time as opposed to all in the beginning, modify champions so they can also rise over time, and set it so that heroes and leaders can age, have children, and die. Governments are being modified to respond to situation with Old One influence, it's no longer the end of the world it's just another dark period - they will be able to struggle against the dark with partisans in occupied POIs, form new radical government types, and even descend into the darkness themselves to try and stem the tide of your evil. Populations and resources have greater variability, mines can run dry, new mines can be found, and the AI has an additional quality to describe "Long Term Planning" versus dealing with immediate problems.
I think that covers the basic existing gameplay changes, as you can see we're going for a "The World Hasn't Ended It's Just Ending" feel, where you can draw out the game and experience it more fully at any of the phases. To support this we're making the changes above and allowing the Final Conflict to instead be recurring conflicts as the world and its prophecies struggle to deal with your influence. The way this extends to the modding community is far more significant, taking all these dependencies and making them configurable allows you to even further craft the behavior of the world and its AI, which is itself further augmented to be able to deal with these situations instead of simply pushing for the Final Conflict.
Outside of these mechanical changes we have a lot of Content that we're adding both to make the player's Old One more interesting in periods of occupation as well as letting the Heroes and Leaders of the world go to more extremes. On the Hero and Leader side there are a lot of extreme measures to be taken as the world darkens, with the implications of Ancient Power setting some kingdoms on a path to corruption and ruin and others to pious extremism. With the Agents you'll be able to contend with the difficulties of occupation and put them in the roles of administrators, brutal if you want or try and take a softer touch and convince the populace how lucky they are not to be orc food.
Tl;dr Mechanics to change the flow of the game + content to flesh it out
EDIT: I forgot, we're adding cyclical gameplay - so when you end a game with your Old One (either by being sealed away or being victorious) you can import some of the the settings of the previous world.