Mount and Blade II: Bannerlord is a game all about building up your prestige in a medieval world. Through war and diplomacy, the player meets various challenges and builds their army to a pinnacle of power. As you increase the power of your Clan and gain renown in the world, your standing among the other Clans and kingdoms will increase, granting you various boons. One of the boons you gain through building your titular empire is ruling over others. And like many other medieval games, you can’t rule the entire world on your own. Vassals, or lesser lords that hold power over a small area and answer to you, are a big part of Mount and Blade II: Bannerlord.
To obtain vassals in Mount and Blade II: Bannerlord, you will need to essentially steal them from other kingdoms. Players looking to build their stable of vassals will need to go to war with another Clan to make it possible to snag their vassals as your own. When you are at war with another faction, use the in-game encyclopedia and head to the page for that Clan. Check the stat for which clans they have as vassals, those are your targets.
The first step to grab them is to start attacking and taking their territory, meaning their villages and castles. That same encyclopedia section should list the names of the settlements you want to target, to make the process easier. Once you have taken some of their territories, your next step is to take on the task of hunting down the leader of that particular minor faction. Speak to the ruler rather than attacking them and you should have an option to invite them to be your vassal.
The chance of getting a minor Clan to join your side is affected by a variety of factors. It appears that the combination of the value of territory and relative military force has a pretty big impact here. most vassal candidates won’t surrender their autonomy easily and will request something of their new liege lord. It may be something as simple as a cash payment, or more complex like a system of alliances or territory transfers in their favor.