Oathbinding
From Norse Angels
Oaths and bonds are important in the Nine Realms. Oaths can only be sworn willingly, but are binding once done so. Oaths can be used to ensure cooperation with someone you distrust, or to create confidence in you, or as a show of bravado. Breaking an Oath will result in severe consequences, decided by the Norns.
An Oath can be as simple or as complicated as you like, but the letter of the oath is what binds you, not the spirit. Oaths can be one-sided - it's perfectly acceptable for someone to swear an Oath expecting nothing in return, or to demand an Oath just to prove loyalty.
For an Oath to be binding, it must be sworn in the presence of a being of power, preferably a Norn, but another character played by a referee will usually be acceptable.
A common use of Oaths is to enforce the results of a Flyting. For example an Oath of the form "We shall Flyt, and the loser swears to ...".
Oaths can be formally broken by publicly declaring it so, as well as, obviously, by breaking the Oath with your actions. If a player breaks an Oath they've made they should tell a referee; you aren't required to tell anyone else.
An Oath is only broken if the swearer willingly does so. Being compelled to do something that breaks an oath doesn't count, nor does breaking an oath due to the effects of your Deviance.