The feudal system from both the Middle Ages and Crusader Kings III revolves around Vassals, characters who are granted by a Liege lower-ranked Titles to more easily manage the realm in exchange for a cut of their Taxes and Levies. Each Vassal can be a Liege towards its own set of Vassals, as long as lower title ranks exist.
The amount of taxes and levies granted by a Vassal to their Liege depends on their Government type:
- Feudal Vassals provide taxes and levies based on their individual Contracts, with minimum amounts determined by Crown Authority.
- Tribal Vassals provide taxes and levies based on the Liege's Level of Fame, with minimum amounts determined by Tribal Authority.
- All other Vassals provide taxes and levies based on their Opinion towards their Liege, with minimum amounts determined by Crown Authority.
As long as Opinion is at least +1, all Vassals will provide the maximum amount of taxes and levies.
Vassal Limit
The Vassal Limit is the number of direct Count Vassals a ruler can have without penalties and scales with the rank of the ruler's Primary Title. A character can avoid going over the Vassal Limit by creating Duke Vassals and transferring Count Vassals to them.
Powerful Vassals
In each realm, Vassals with the highest tax income and number of levies are designated as Powerful Vassals, Vassals who expect to be part of the Liege's Council and will have -40 
Opinion of their Liege if they're not. The number of Powerful Vassals a Liege will have depends on the rank of their primary title. In elective succession types, Powerful Vassals have more votes than regular Vassals. They're also much harder to use the Sway Scheme on.
In order for the succession law of a realm to be changed, all Powerful Vassals must either have positive Opinion of the Liege, be Terrified or be Imprisoned.
Factions
Factions are organized groups that are united against their Liege for a common purpose. As long as their issue isn't resolved they will keep growing until they will be large enough to deliver an ultimatum to the liege.
All Factions have two important values: Military Power and Discontent.
- Military Power is the ratio between the combined military strength of all Faction members and the military strength of the liege. When the ratio is above 80%, the Faction will gain Discontent; when it is below the threshold, the Faction will lose Discontent.
- Discontent is a measure of how close the Faction is to sending their ultimatum.
A Faction will deliver its ultimatum shortly after Discontent reaches 100%. It can also send it early if the liege unjustly imprisons someone. If the ultimatum is accepted the liege will gain -20 
Dread. If it is refused it will start a civil war.
There are 5 types of Factions:
| Type | Ultimatum | Military Power | Members | Requires Military Power for Discontent |
|---|---|---|---|---|
 Independence
|
|
Members' armies |  Vassals
|
|
 Claimant
|
|
Members' armies | Vassals
|
|
 Liberty
|
|
Members' armies | Vassals
|
|
 Populists
|
|
25% to 50% of each County's  Levies
|
 Counties
|
|
 Peasant Rabble
|
|
50% to 100% of each County's Levies
|
Counties
|
|
Prestige
Weak Hook on the Claimant
ControlVassals cannot join a Faction against a liege that has an Alliance with them or has a Hook on them. They also can't join a Faction against a Friend, Lover or someone they're Terrified of.
Civil Wars
If a Faction's ultimatum is refused, it will start a Civil War. During a Civil War, Faction members stop providing taxes and levies to the liege and their liege loses access to certain powers such as imprisonment. All Faction members will turn hostile to both the liege and all vassals that did not join the Faction, though they will focus on fighting the liege.
- If the Civil War ends in White Peace, the Liege will gain an imprisonment reason against all Faction members.
- If the Civil War is won by the Vassals, they will enforce the Faction's ultimatum.
- If the Civil War is won by the Liege, all Faction members are imprisoned and the Liege gains +20 Dread. If the Faction was caused by Popular Opinion, each rebelling County will gain +20 Popular Opinion for 10 years.