At long last, the first big expansion pack for Civilization VIis incoming.

As any long-time fan will tell you, that's big news. Civilization expansion packs tend to fundamentally change core game rules, usually for the better. And Civ VI's upcoming Rise and Fallcontinues that tradition.

A Tuesday morning trailer from developer Firaxis Games delivered a cinematic expression of the new content, but there's also a full-blown breakdown of features from Anton Strenger, the add-on's lead designer.

Here's how the next major chapter for Civilization VIlooks so far....

Loyalty matters -- big time

Rise and Fallplaces a particular emphasis on giving players a wider range of non-combat options for expanding their empires. Loyalty is central to that.

The new system forces players to think about how their actions might be viewed by people around the world. Drive your loyalty too low and you risk losing some of your own cities. Make people in your own civ love you lots and other civs will take notice, potentially flipping nearby cities over to your side.

Loyalty also feeds into the return of the Golden Age, which was realized in past games as a multi-turn period during which your chosen civ would just generally do better at everything. Rise and Fallre-thinks the Golden Age as more of a strategic play, and balances its effects with the all-new Dark Age.

Strenger describes Golden and Dark Ages as a sort of "loyalty bomb," similar to the Great Person-triggered culture bombs of past games. Entering into a Golden Age gives you all sorts of bonuses -- including a huge loyalty boost -- but it also makes it tougher to trigger another one at a later point in the game.

Dark Ages, on the other hand, test the loyalty of your people. But these periods also open up access to special, civ-influencing policies, and going through one makes it easier to trigger a Golden Age later. On top of that, going through a Dark Age also make it possible to enter into an all-new Heroic Age, which sounds like a superpowered Golden Age.

As Strenger describes it, Golden/Dark Ages give players an opportunity to change their strategies during a given game.

Public figures

Civilization VI: Rise and Fallalso revises city governors. In past games, "governor" was just a generic term for putting a selected city on autopilot. If you didn't want to micromanage things like production or worker assignments, an invisible governor would handle it for you.

Rise and Fallturns governors into individuals, each with their own strengths, weaknesses, and progression path. They are no longer a one-per-city proposition. It's probably more helpful to think of them in the same terms as Great People: You'll only see a limited number over the course of a game, but each one has a meaningful impact.

In the space of a given game you won't be able to earn more than seven Governors. Just like military units, each one has its own skill tree. As you play, you earn points -- Governor Titles -- that can be spent on obtaining new Governors or leveling up any you already have.

Strenger describes Governors as "a way to specialize your cities." You choose where they go and what they work on, though you'll also need to account for the roles they're best-suited to tackle. A Governor who boosts Wonder production, for example, might not be super helpful in your outlier cities where infrastructure production is still lagging.

Diplomacy 2.0

Every Civfan faces the same dilemma: Military action is often the easiest route to victory. As with most of the series' expansion packs, Rise and Fallattempts to address that. Loyalty, and the potential for cities to switch sides, is one facet of that shift. But diplomacy also gets a significant makeover.

Rise and Falllets you build alliances with other civs based around specific pursuits. Research, Military, Economic, Cultural, and Religious alliances all provide different benefits, but the core idea is the same: You're no longer just trading goods and forming military partnerships.

More than that, alliances grow stronger over time. Strenger's offers the example of Research Alliances: At Level 1, both allied civs receive a Science bonus on any trade routes between them; Level 2 adds an additional Tech Boost to the mix; and at Level 3, each civ receives bonuses when they research the same tech together, or when one researches a tech that the other has already discovered.

To balance these bonuses, civs are limited to one of each alliance type at any given time.

Rise and Fallalso tweaks Civilization VI's diplomatic landscape with new Emergencies. These global events are triggered by one of the more powerful civs rocking the planet with some major event, such as the dropping of a nuke.

When an Emergency breaks out, all the other civs are invited to either join in on completing a shared objective or pass completely. Achieving the objective unlocks permanent bonuses for all participating civs; failure gives the triggering civ -- the bomb-dropper, in the nuke example -- a bonus.

Practically speaking, Emergencies amount to a check on dominant players that should help to create more balanced games. In these one vs. many scenarios, the many have an opportunity to shut down the one's sure-thing win. Even if they fail and the dominant player's position is only cemented, the objective-driven approach promises to inject more flavor into games that, in the past, would have seemed like lost causes.

And then some....

Alongside all of these core system tweaks, Rise and Fallintroduces an assortment of yet-to-be-revealed new civilizations and leaders. There are also Historic Moments -- as the trailer hints at -- which don't affect the strategic game so much, but lend more flavor to your personal journey.

Historic Moments are basically achievements that you can unlock on a per-game basis. They're all -- "more than 100," according to Strenger -- important civ events, like circumnavigating the globe, or founding a new religion.

Functionally, unlocking an Historic Moment pushes you closer to achieving a Golden Age for your civ. But these events are also recorded on your game's timeline, lending extra flavor to the post-game recap of your progress through time.

Civilization VI: Rise and Fallwill be out on Feb. 8, 2018 and -- based on these first details -- it's looking like a smart, thoughtful expansion of an already-great game.