In the eleventh century the political map of what is now Belgium had not yet hardened into the duchies and counties that the late Middle Ages would inherit. The Hesbaye region, Haspengouw in Dutch, was an ancient grain-growing plain spread across what later became parts of Liège, Limburg, Brabant, and Walloon Brabant. Within it, names of small counties came and went as families rose and married into one another. There was a county of Avernas south of Sint-Truiden, mentioned in two tenth-century documents and then lost to history. There was a widow named Erlinde or Herlendis who in 1021 styled herself Countess of Duras, but later documents would call her instead a countess of Jodoigne. Lands were inherited in pieces, intermingled with the holdings of larger neighbors, and titles attached to specific functions more than to clean blocks of territory.

The first certain count of Duras was Giselbert, son of an Otto who was himself sometimes called a count of Loon, the brother of the man whose descendants would rule the much larger neighboring county. Giselbert took up the under-advocacy of Saint Trudo's, and the office passed to his son, the second Count Otto. The office and the title traveled together, as if Duras existed mainly to give a legal foothold to a particular family's role at the abbey. When Otto II died with only a daughter, Juliane, she took her inheritance into the family of the Counts of Montaigu through marriage to Godfried of Clermont. Their son Gilles died childless. Gilles's brother Conon held both Montaigu and Duras for a time. When his line ended, the county reverted to the Prince-Bishopric of Liège, which sold it to the Counts of Loon. The distinct entity called Duras was finished.

These under-advocates were not gentle protectors. They held the secular powers the abbey could not exercise itself, and they were not shy about using them. The medieval chronicle of Saint Trudo's, the Gesta Abbatum Trudonensium, returns again and again to the conflicts that grew up between the subadvocatus and the very monks he was supposed to protect, the tenants whose rents he collected, and the senior advocatus above him, the Duke of Limburg and later the Duke of Brabant. The same pattern repeated across Europe in the twelfth century. A position that began as service to the church became, in many hands, a hereditary lordship that the church had no real ability to remove. The Counts of Duras were among the abuses the abbey suffered, and also among the families it could not do without.

The eighteenth-century castle that bears the family's name still stands in the small village of Duras, today part of Sint-Truiden in Belgian Limburg. It is not the medieval keep where Giselbert and the Ottos lived. That building is long gone, replaced in the centuries after the county itself dissolved. But the geography survives. The villages whose tithes the Gesta argued over are still villages. Saint Trudo's Abbey, the engine that called this county into being, gave its name to the town of Sint-Truiden and to the Limburg country that grew up around it. Even Jodoigne, the lordship the family inherited through the mysterious widow Erlinde, is still a town in Walloon Brabant on the line where the language border runs. The county died. The roads remember it.