Provided they can maintain Cohesion by using Envoys and voting together, a Federation will steadily gain XP and unlock shared bonuses as they rise through 5 levels. Additionally, with the Fleet Contribution Law, each member of the Federation will contribute ships to an upkeep-free Federation Fleet, which uses the best ship designs in Stellaris available to any member. The simplest benefit is safety in numbers, as all members of the Federation will support each other in defensive wars, and can vote to join offensive wars as well.

There are many advantages to forming a Federation in Stellaris, both with and without the Federations DLC. This process is further complicated when it comes to inviting additional Empires to an existing Federation, as by default all members will get a vote on who can join, giving players less control over the system. Policies and Ethics are often the biggest factors in whether an Empire is willing to join, with a Spiritualist Empire less likely to join a Materialist Federation, and a Pacifist Empire unlikely to ally themselves with an Empire that allows wars of aggression. Sending an Envoy to Improve Relations will increase the Opinion of the target Empire, but Opinion alone is unlikely to convince an Empire to join. Some Xenophilic Empires will be predisposed to seek membership in a Federation, others will need more convincing. However, unlocking the ability to form a Federation and actually founding one are two very different things, and players must cultivate good relationships with their AI neighbors before they can persuade them to join. With this Tradition unlocked, all players need to do is open the diplomacy screen with an AI or player-controlled Empire in Stellaris and select Invite to Federation.

Alternatively, any Empire that doesn't have the Fanatic Purifier, Devouring Swarm, or Inward Perfection Civics can attempt to form a Federation after completing The Federation in the Diplomacy Tradition tree. The easiest way to form a Federation in Stellaris is to start as one using either the Common Ground or Hegemon Stellaris Origins, both of which require the Federations DLC.

There are four routes to creating a Federation in Stellaris, though two of them are rare events that are unlikely to occur in every game.

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