Limerance Dogma 2
"The oaths between liege and vassal are sacred. This is the fidelity between Limerance and Gloria." -- The First Law of Limerance.
While oaths between a liege and vassal have existed long before the Compact and can take several different distinct forms, with the individual oaths varying based upon the different regions of Arvum and some unique traditions in each of the old five kingdoms, but ultimately they all have strong similarities and all are sworn before Limerance, even in the shamanistic Northlands. In fact, some claim the Valardinian Crusades from the Oathlands against the Northlands started in large part simply from the then refusal of northern houses to swear upon Limerance when making oaths, and a few broken oaths over relatively minor matters being taken as a slight against the Pantheon.
The term 'vassal' is used but it is imprecise, as really it can refer to three different groups, each with their own distinct oaths, vows and pledges to a liege lord. The three separate groups are: Banner lords, who are granted their own domains in service to a liege. Sworn swords, such as knights, who are tied to the liege's own demesne (domain) and typically live on and fight for it. And commoners who live and work on the domain. All three are vassals, but they have distinctly different obligations and oaths accordingly.
For a bannerman/banner lord, they are granted their own peerage (typically carved from the liege's own lands), ennobled (if not already noble) and in exchange for being granted those lands in perpetuity they take oaths of service. The wording differs heavily, but it always demands that the new Peer of the Realm answer the call to war, defend their own commoners under their care, and share the wealth of their lands (pay taxes above). The first and second part are important, and are typically kept vague, as it notes that there is a balance in a new lord defending their own lands from all threats while answering the call in time of war, so traditionally the judgment on being able to meet both obligations simultaneously is entirely up to the new lord's discretion. If she feels she can only safely commit 20 percent of her forces to banners being raised and must keep eighty percent at home because of imminent attack, she cannot reasonably be called an oathbreaker for it, as they are two separate oaths that they need to both meet. This, of course, leads to constant friction between bannermen and their liege lords.
Example oaths on the creation of a new peerage from a liege, "I grant you these lands, take your house into my service. I may call upon you in war, I may ask you to share your land's incomes, but I swear before Limerance I shall never call upon you to perform a task that would bring dishonor. The affairs of your house are your own, and I will trust to your house to act with honor."
A new bannerman's oath in turn would often appear as, "For myself and my house, I swear before Limerance when you call us to war, our banner will fly along yours and our swords will be at your side. I swear I shall defend my land and my people, and pass no unjust laws in my domain. I swear you will always be an honored guest in our lands, and no less than one thirteenth of our incomes will be yours by rights. I swear I shall take no other vows that would place service to another above you, unless you release me from my vows."
It is important to note that lands are granted to a house in perpetuity, and not to an individual, and then the house is expected to make laws (consistent with the conventional morality of the Faith of the Pantheon) for their own domain, including succession. Therefore, it is considered a massive overstep for any lord to attempt to control succession in a vassal's house unless, pointedly, a claimant asks for a liege to intercede (which is the most common way for a succession crisis to be resolved).
An oath between a liege and a sworn sword, typically knighting a soldier in their service, is different. As a servant living on the liege's own domain, that is a much closer, more personal form of service, with a direct employment and the expectation that the sworn sword can be given any reasonable order or task. Those sorts of oaths of service are generally understood to be life long unless the liege explicitly states otherwise, and one cannot leave the service without being released and not be considered an oathbreaker. Fortunately for many knights, most lieges are reasonable if someone wishes to seek service elsewhere and release them from their vows, rather than keep an unhappy armed retainer of questionable loyalty.
A lord accepting such an oath would often say a version of: "I ask you to enter into my service and my house, and to fight by my side. I swear by Limerance and Gloria that I will ask no task of you that brings you dishonor. I swear I will reward fidelity with fidelity, and never be false with you."
And a knight taking an oath of service would typically answer, "Before Limerance and Gloria, I swear my sword to your service. I swear to complete any lawful task asked of me, obey your laws, and stand fast even if it should mean my death. I will take no vows that may come before my service to you, and serve until my death or I am released from your service."
For commoners, vows are simple, with an agreement to obey all laws on the land, answer the call if called to war by levy, and to seek no service with another until released. Notably, commoners are free to travel, but would technically not be freed to seek service with another or change their fealty until released, but for becoming Crownsworn that is considered perfunctory, and most lords do not concern themselves with commoners switching fealty except in the most distant way. This also makes travel to Arx more sensible as an option for many wishing to leave the service of an abusive lord, as representatives of nearly every house are in the city who can release them from their oath, though the Faith of the Pantheon typically comes to the rescue of many commoners in such situations. As any seraph could also judge any oath to a lord that was abusive as invalid, and declaring the Oath void, freeing the commoner to seek service in the new domain they are in, or a commoner could also become godsworn, as most of the Faith would agree that an oath to the gods would render oaths to a mortal liege invalid. There is some disagreement on that last point due to the explicit oath to 'not seek service with another that would come between the liege', but the general understanding is it does not apply to the Faith, and the Faith has long since won that argument.