Every Empire has traditions and customs. But these customs and traditions can spread, from Territory to Territory, reaching neighboring Empires and eventually spreading across the world. In modern terms, a fashion craze going global would be one example. In Humankind, this propagation of customs to other places is known as Influence.
Stories are the building blocks of any society and the cement that holds power structures together: your Empire’s Influence stock represents the legitimacy of your rule.
You can spend your Influence stock to claim Territories and Cultural Wonders, create Cities, enact Civics, propose Treaties and more. Having too many Cities in your Empire also drains your Influence: be careful not to let it get too low, as if your stock falls below zero your rule will be considered illegitimate by your people and your Cities will start to lose Stability !
Once you have paid the Influence cost required to unlock a Cultural Wonder, say the Hanging Gardens of Babylon, your Empire will be the only one allowed to build it. Each Wonder can be built only once, and you won’t be able to lay claim to a new Cultural Wonder until you’ve finished building the previous one. Unlike most other Constructible Elements, multiple Cities can provide progress towards the completion of a single Cultural Wonder, regardless of where the Wonder is placed in your Empire.
To propagate and enrich your own traditions and customs, you need to generate Influence. Some specific situations will increase your Influence stock without affecting your Sphere of Influence though: in the Neolithic era for instance, you can increase your Influence stock by hunting Animals and collecting Curiosities.
Influence is mostly generated at Territory-level however, as its effects are closely tied to the map: building the Hanging Gardens of Babylon will add to your Influence stock each turn, but it will also expand your Sphere of Influence out from the specific Territory where you built said Hanging Gardens.
Completing any Cultural Wonder, as well as certain Districts, Infrastructures and Public Ceremonies will increase the Influence generated by your Territories each turn. Certain Legacy Traits, Religion Tenets, Technologies and Civics can also increase the Influence production of your Territories. You can see a recap of how much a City’s Territories are producing by selecting the City.
The set of Territories under the cultural domination of an Empire is referred to as its Sphere of Influence. To expand this Sphere of Influence, you must improve the Influence production of your Territories until it is higher than that of adjacent Territories.
A Territory can only be part of a single Empire’s Sphere of Influence at any given time, but multiple Empires can simultaneously be vying to add it to their Sphere. Each of these pretenders has an “impact” on the Territory that is based on the Influence production of their nearby Territories, with the impact of more distant Territories’ Influence productions counting for less than those of adjacent Territories.
If you’re able to keep your impact sufficiently high above anyone else’s for a set number of turns then the Territory is added to your Sphere of Influence. Opponents are informed when this “conversion” begins, so have time to respond either militarily or by increasing their Influence production.
Soft power is a great way of justifying invasions: once another Empire’s Territory is in your Sphere of Influence a Grievance against them will be generated which you can use to Demand it from them! Territories in your Sphere will also affect the War Support your opponent has if a War ends up being declared.
Territories that are part of your Empire’s Sphere of Influence do not confer direct economic advantages, but you’ll need to add them to your Sphere first before more distant Territories can be affected. In addition, adding an Independent People to your Sphere of Influence will passively improve your relations with them each turn.
Owning Territories inside another Empire’s Sphere of Influence might seem harmful for the reasons listed above, but you can also benefit from it!
If Territories belonging to one of your Cities remain in a friendly Empire’s Sphere of Influence, then you will eventually have the opportunity to acquire one of their Technologies, for a price. You can also forgo the opportunity and receive a small Science boost instead.
Acquiring Science or Technologies from another Empire thanks to their Influence is called Osmosis.
Watch out though, you will only be offered Technologies if your Ideological Proximity with the influencing Empire is sufficiently high: if it is too low then you may be pressed to adopt their Civics choices instead!
It is of course possible to refuse this change, but in this case, the influenced City receives a Status which temporarily lowers its Stability.