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. Every character can have at most one liege.
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 feudal contracts.
- Tribal vassals provide taxes and levies based on the liege's level of fame, with minimum amounts determined by tribal authority.
- Clan vassals provide taxes and levies based on their
opinion towards their liege, with minimum amounts determined by crown authority. - Theocracies provide taxes and levies based on the liege's level of devotion.
- Republic vassals always provide 20% taxes and 10% levies to their liege.
- Rulers whose faith has the Theocratic doctrine lease their temple holdings to a Realm Priest, providing increased taxes and levies with higher opinion.
封臣上限
封臣上限是统治者可以无惩罚拥有的直属封臣（除去男爵）数。其主要基于统治者主头衔的等级，并且可以通过法律和特质增加。[1]
| 条件 | 封臣上限 |
|---|---|
 是  公爵
|
+20 |
是  国王
|
+40 |
是  皇帝
|
+60 |
是  头衔继承法帝国选侯制
|
+20 |
拥有特质  最伟大的汗
|
+20 |
角色可以通过创建公爵封臣，使用转封封臣互动将伯爵封臣转移给他们来避免超出封臣上限。角色的封臣上限可以在领地菜单（F2)右下方查看。
强力封臣
领地内，拥有最多 税收和 征召兵的封臣被指定为强力封臣。强力封臣期望得到领主的内阁职位，如果他们不是内阁成员将对领主 -40 好感。领主将拥有的强力封臣数将取决于他们主头衔的等级：
| 等级 | 强力封臣 |
|---|---|
 伯爵
|
3 |
| 公爵
|
4 |
| 国王
|
5 |
| 皇帝
|
5 |
选举继承法类型下，强力封臣相比一般封臣有更多可投选票。拉拢他们也更困难。为了更改领地的继承法，需要所有强力封臣对领主有 正面 好感，或者 
畏惧领主或者被囚禁。
派系
派系是为了共同目标而联合反对领主的有组织团体。只要他们的问题没有被解决，他们将不断壮大，直到足够向领主发出最后通牒。
所有派系（除了乌合之众）有两个重要数值：军力和不满。
- 军力是派系所有成员军力总和与领主军力之比。当比值超过80%，派系将获得不满；当低于这个阈值，派系失去不满。
- 不满衡量派系离发出最后通牒还有多近。
派系在不满达到100%不久后发出最后通牒。如果领主不公正地囚禁某人，也可以提早发出最后通牒。如果最后通牒被接受，领主将 -20 
恐怖值。如果被拒绝，将导致内战。
有5种派系：
| 类型 | 最后通牒 | 军力 | 成员 | 不满需要军力 |
|---|---|---|---|---|
 独立
|
|
成员的军队 |  封臣
|
|
 宣称者
|
|
成员的军队 | 封臣
|
|
 自由权
|
|
成员的军队 | 封臣
|
|
 民粹主义
|
|
每个伯爵领25%至50%的 征召兵
|
伯爵领
|
|
 乌合之众
|
每个伯爵领50%至100%的 征召兵
|
伯爵领
|
|
封臣不能加入反对领主的派系，如果：
内战
如果派系的最后通牒被拒绝，将导致一场内战。内战期间，派系成员停止向领主提供税收和征召兵，并且他们的领主失去某些权力，例如囚禁。所有派系成员将与领主以及没有参加此派系的所有封臣敌对，即使他们专注于同领主作战。
- 如果内战无条件和平，领主将获得对所有派系成员的囚禁理由。
- 如果封臣赢得内战，他们将强制执行派系的最后通牒。
- 如果领主赢得内战，所有派系成员被囚禁，领主获得 +20 恐怖值。如果派系产生于 公众好感度，每个叛乱伯爵领将获得持续10年的 +20 公众好感度。
Leased Holdings
When a ruler's religion has the Theocratic Doctrine, temples are leased to a realm priest. The realm priest provides their liege with taxes and levies based on their opinion. The minimum is at 0 opinion, where no taxes or levies are provided, and the maximum is at 50 opinion, where 50% of the taxes and 100% of the levies are provided.
For vassals of the same religion, a vassal's income from their realm priest's church holdings are not directly taxed by their liege. The vassal's realm priest provides their liege's realm priest with 25% of their temples' taxes, and 15% of their temples' levies. This vassal realm priest contribution is provided by the liege realm priest to the liege at the same rate as directly leased holdings. Vassals of different religions are skipped in the hierarchy of lease payments.
Example:
You are a duke with one county within your domain. That county has a temple with a tax of 1 gold and a levy of 300. At 50 opinion with your realm priest, he will provide you with 0.5 gold in taxes and 300 levy.
You also have a vassal count who has one county with one temple as well. That temple has the same tax of 1 gold and levy of 300. Your vassal's realm priest provides your realm priest with 0.25 gold and 45 levy, before he splits the rest with the count based on his opinion of the count. Then, your realm priest splits this contribution with you, for a final .125 gold and 45 levy from your vassal's temple. The count will receive a maximum of .375 gold (50% of the remaining .75 gold), and 255 levy (100% of the remaining 255) from their realm priest at 50+ opinion.
References
- ↑
game\common\laws\01_title_succession_laws.txt，game\common\traits\00_traits.txt