An Empire is a group of planets and star systems that are ruled by the same government and controlled by a single player. Empires may have a variety of governments such as a democracy, republic, oligarchy, or imperial rule.
Ethos is the most defining feature of a space empire; it affects the behavior of AI empires, likely technologies, available policies and edicts, valid government types, the opinions of other empires, and - perhaps most importantly - it provides the fuel for internal strife in large and diverse empires.
It should be noted that the name of the player empire can always be changed in the government window.
The capital is the ruling seat of an empire. Initially the homeworld of the primary species, an empire's capital can be moved once every 10 years for a cost of 250 influence. An empire's capital enjoys the following benefits:
- -10% ethics divergence
- +10% happiness
- +50% planet border extrusion
- can build the Empire Capital-Complex (moving the capital downgrades it)
An empire's capital planet and system feature star corners on the system and galaxy maps.
Core systems are the systems whereby planets are directly managed by the player. The base number of core sector systems is 5. It is increased by some government types and through research.
The following table may contain outdated information that is inaccurate for the current version of the game. The last version it was verified as up to date for was 1.3.
If the number of directly controlled systems exceeds this limit the empire gets the modifier “Inefficient Planet Management” with the following effects:
At or before this point, it is best to start delegating excess planets into Sectors. Since a single star-system may contain multiple colonized planets, it is natural for the player to retain control of systems with multiple inhabited planets.
The Empire capital is always part of the core systems and cannot be transferred to sectors.
A Sector is a semi-independent administrative region under the control of a Governor. It will govern itself, though the empire remains responsible for the defense and protection of its sectors and can issue some priorities and orders to the sector government.
Each sector has its own stock of energy and minerals. These stocks will be filled with sources within the sector's borders, except that some of its income may be sent to the national stockpile depending on what tax level is selected for it. The sector's stocks can also be boosted in 100 unit increments from the national stockpile. Science and influence income go to the empire regardless of tax. Strategic resources can be used by a sector only if the sector itself has them; any surplus goes to the empire, and sectors cannot use resources from other sectors or core worlds. Sectors ignore the influence cost of buildings so that it can upgrade the capital buildings from ship shelter up to a planetary capital if the other requirements are met. Frontier outposts controlled by sectors do continue to cost imperial Influence to maintain.
Sectors remain an integrated part of the empire, but handle development of planets and the construction of stations and defensive armies within their region themselves. What exactly they build is influenced by the focus set for them: military (focusing on defense stations), industrial (focusing on minerals), scientific, or economic (focusing on energy). They can be permitted or forbidden to replace existing buildings and/or requested to respect existing resource deposits. Note, that sectors prefer to maximize food output on new colonies so they reach their maximum population faster, if redevelopment is forbidden they will be stuck with excessive farms. Sectors do not possess or build any military fleets or offensive armies of their own, so the empire is responsible for their defense and protection.
The exact limit for direct control of planets depends on various factors, such as government type and technologies. Sectors are created by clicking on the empire tab at the top left of the screen. Sectors can be created and removed at will and assigned a name and sector capital of the player's choice. Star systems can be added to and exchanged between sectors at any time, but each sector must always be a single contiguous region of connected space. If a sector becomes non-contiguous due to conquest or other actions a penalty will be assessed on its production.
The technologies to increase the maximum number core worlds and sectors are both techs that may be researched repeatedly, although at increasing cost. Sector limit gets increased by 1 for every 4 owned planets.
Removing star systems from a sector costs 25 and removing sectors costs 100. However, if the sector is smaller than 4 star systems, it costs less influence to remove each star system manually until the sector is removed. There appear to be no limits to the number of stars within a given sector.
As an empire grows, it will increase its sphere of influence around the star systems in its immediate area. This area, shaded on the galaxy map in the empire's color, represents an empire's territory. Civilian stations may only be built and exploited within this sphere of influence. If the empire's borders expand or contract, any civilian station in gained or lost star systems will change ownership accordingly.
The sphere of influence is expanded by building colonies or frontier outposts in star systems near the edge of or outside your sphere of influence. If you build one too far from your borders, your sphere of influence may not be contiguous. Also, certain technologies will increase the empire's sphere of influence. Finally, Despotic Empire and Star Empire governments have a larger border extrusion.
Border spread works volumetrically. As an empire becomes more dense and grows, its borders also appear to spill outward.
Removing colonies or frontier outposts from within the empire's well-established borders may affect the outer border unpredictably.
There are certain research subjects that allow for borders to be expanded.
Due to the 3D nature of the galaxy, systems can appear to be in an empire but actually not. The more precise way to check for border belonging is to look at the projection of the system represented by the hexagon.
Newly colonized planets begin with an initially small border, expanding slowly with time. Colony borders are further expanded by 15% for each Pop beyond 1. As mentioned above, the homeworld has an additional 50% bonus to its border range.
Frontier Outposts can be built on any surveyed star using a construction ship. Expanding the borders by building too many frontier outposts may be seen as hostile by neighboring species.
Frontier Outposts have a base cost of 100 and 30 to build, with the cost increasing according to how far away the outpost is relative to your empire's current borders. In addition, they require 3 and 1 per month to maintain.
Borders are crucial, especially during the initial stages of the game when they can be used to secure planets for future colonization during the period when colonization is not yet possible. Border growth can also provide additional mining resources as well as inhibit the potential expansion of other empires. Frontier outposts, despite the hefty influence costs, are the easiest way to secure large borders, and should be the primary influence dump early game. They can be eventually disbanded once planets can sustain the respective borders.
Borders expand and contract throughout the game based on many different factors. These border changes are taking place constantly as you and your governors make decisions. Therefore, it is possible that there may be resource-rich systems that quietly come under your control as your empire gains power and its borders dynamically expand. Because you are not notified when new systems are acquired as part of this silent border expansion, you should frequently examine critical border sections to look for new colonization and exploitation opportunities.
The converse (losing systems due to AI empires establishing colonies/ frontier outposts at border areas where your empire's presence is weak) is true as well.
Victory conditions are predefined goals that ensure victory of the game.
There are three ways to achieve victory in Stellaris:
- Domination, which requires you to own 40% of all colonizable planets. Planets owned by vassals count but those owned by allies and Federation members do not.
- Conquest, which requires to conquer or subjugate all other empires. Fallen empires do not need to be conquered.
- Federation, which require the federation which you're a part of to own 60% of all colonizable planets.
Any empire, even an AI empire, can end up meeting the victory conditions, though the AI ignores their existence and may thus only win as a result of other priorities.
The game can be continued even after an empire claims victory.