The feudal system of Arvum has existed since before the Reckoning. While numerous houses have oral accounts of lineages stretching back more than a thousand years, no house claims to have any records of an era before the days when a great house dominated a region and acepted the fealty of bannermen in exchange for peace. Before the days of the Compact, the great houses ruled as independent monarchs in their own demesne (domains), taking oaths of loyalty and service from those that lived within their demesne and training many into sworn swords. Some vassals in turn are granted lands to become bannermen under the system of enfeoffment, creating new noble houses to serve and manage their own separate subservient demesnes and creating a tree of noble families all ultimately under a great house.
Even now in the days of the Compact, the feudal system is largely unchanged, with the voice of lords in their own domains carrying the full weight of law. While commoners sworn to a lord might technically seek recourse by petitioning the liege of their lord, in practice most lieges would seldom ever intervene in the internal disputes of one of their lord bannermen. In return for this autonomy, lieges tax their vassals and call upon their support in war, though the oaths of loyalty are only taken directly to their immediate liege. Dukes are sworn to serve the prince ruling a great house, and a marquis might be sworn to a duke in turn, but the first loyalty for that same marquis would be to the duke and his immediate liege and not to the prince- a small distinction that is ever so important whenever a liege quarrels with his own vassals and thusly his vassal's vassals.
Culturally, the rights of the people in the demesne vary by the great house, but there are extremely few restrictions upon the legal authority of a lord within his own demesne. Inside Arx itself, where a great many of the populace are crownsworn and owe loyalty only to the crown, the commons tend to enjoy a greater degree of freedom and Peers of the Realm can expect potential consequences for actions against commoners not within their demesnes. More than one minor noble has been killed for actions against commoners who happened to be proteges of far more powerful patrons.
Succession varies from great house to house, but only House Thrax and its vassal houses still hold to male primogeniture. The head of a noble house is well within his rights to declare an heir not the traditional eldest legitimate child, but to do so invites the potential of an ugly fight of succession after their death if the normal standard successor decides to dispute the claim (the most common cause for civil wars in a great house). In cases when the head of a house dies without issue, often the liege will intervene and name a suitable successor. In the case of the Sovereign of the Compact, when no such liege exists above the reigning monarch, there has only been a scant few examples when the king or queen perished without issue and immediate family, leading to the high lords voting a potential successor in a great council among the Assembly of Peers.