If a certain noble takes upon an estate or a position of Lord within a duchy, or a duchy within a realm, in essence they swear allegiance to their Lord, Duke or Ruler.
Historically in a feudal society and oath was a certain pledge of allegiance, a noble would swear certain things using certain words.
The knight, Lord or duke relation in BM is very utilitarian, usually just a practical deal to get a better income.
Sometimes however, these bonds of allegiance create interesting situations, political unions or niche groups.
Game mechanic changes over the last years supported messaging your duchy and other things to make this more easy or even possible.
A simple text recording, treaty style format for these bonds of allegiance could be a platform for real oaths, or conditions of allegiance.
Just like our diplomacy treaty system a message could be set up and then signed by both parties making the aliegance official.
Nothing fancy, just an official and public recording of the oath itself, stating how the vassal will serve its lord.
Lords, Dukes or Kings could set up standard or outstanding(individually unique per estate) oaths which only require the signature of a vassal.
This way vassals can still pick estates like they do now, but instead of just shopping for the best income, they can now also shop for the best oath.
Example:
Region Lord A has two available estates, estate 1 has an outstanding oath asking the vassal to swear allegiance as a champion, fighting the lords duels.
Estate 2 asks for a skilled man of the shadows for personal security or special services (infiltrator).
Even a promise to work as a courtier or diplomat could be considered.
A more common oath would be a pledge of military support to his or her vassal.
Perhaps it works easier for estates as for region lord positions or duchies.
But its an interesting addition none the less.
A duke could ask his lords to swear political allegiance as an oath of fealty, promising to vote in his favour if they are able to cast a vote, if not they could still vouch for their duke otherwise.
A duke could even ask or include in his oaths its lords to set up certain specific oaths, adding more special characters to its duchy.
Thus more effectively gaining influence and power inside and or outside the realm.
Its up to the Lord, Duke or ruler to make sure its vassals uphold their oath of fealty, and no game mechanics are further required for this to work.
