Secret Fealty in Stellaris is a new feature introduced as part of the Overlord update, a small addition to your relationship with vassals that has potentially dire consequences should you mismanage your relationships.
Key to the Secret Fealty feature is loyalty, the standard by which Stellaris measures your subject empire’s devotion. Loyal subjects let you exploit them in trade agreements, but take advantage of them too much, and they may start an intergalactic war.
What is Secret Fealty in Stellaris?
Secret Fealty is a new action your subject empires may take if they decide they don’t like you very much after all. Disloyal vassals may swear allegiance to opposing empires, and you likely won’t know it happened until it’s too late (hence being called “secret”).
In most cases, you’ll stumble on the fact through a status description, usually between you and another empire. Vassals who go for a Secret Fealty agreement want their new Overlord to declare war on you in a new type of aggression called Allegiance Wars, in the hopes that the new Overlord will win and can claim the vassal as their own.
In short, your life as an intergalactic warlord is much easier if you’re able to keep your subjects happy.
How does loyalty work in Stellaris?
A number of factors influence vassal loyalty in Stellaris, from the terms of your original contract with the subject empire and the trade deals you broker with them, to whether you declare war on your vassals (don’t do that) or engage in imperial activities the vassal is ideologically opposed to.
Loyalty increases or decreases each month depending on the relationship with the vassal in question, though you can extend a bit more control over it with actions such as pledges of loyalty, which grants a small increase over their monthly loyalty increase.
There are other worthwhile benefits to having loyal subjects, aside from avoiding wars with greedy Overlords. Loyal vassals are more likely to agree to harsher trade deals that don’t necessarily benefit them and generally behave better during negotiations.