The Douglass Concord
In the two centuries since the coup d'etat by Clan Craig of Laphraoig that ousted Clan Douglass from the monarchy, Caledon's fortunes had ebbed; the principality's social and economic dynamism was supplanted by pointless court intrigues that occasionally broke out into armed hostilities.
In the aftermath of the coup, the Mourhead sect of Clan Douglass had fled to start Grand Duchy of Douglass, and rumors abounded that other nobles were thinking of trying their luck outside the Caledonian umbrella.
Prince Simon I, who had ruled for over 23 years, had always been a mediocre ruler - which was several steps improved from his elder brothers, Bruce, Laurence and Roger, who had ruled among them for 14 of the most dissipated, corrupt years in the history of the Principality.
Simon had brought some order to the clan's workings - but he looked at his own children, and saw the extent to which they were a group of bickering bobbleheads, and realized that Caledon needed a major change.
He approached his regent, Colin MacArthur, and formulated a plan; usher the corrupt Derwent and Clyde branches of the Douglass clans into retirement (with a large land grant and a charter for several Douglass-owned enterprises to keep the relatives busy), the negotiation of a treaty with his long-estranged distant relatives in the Mourhead clan on the Grand Duchy of Douglass bringing those three systems into the Principality, and the turning of the monarchy over to Clan MacArthur of Inverloch.
It was not an easy process - it involved the careful delegation of power to a coalition of several clans in support of the MacArthurs (the Stuarts of Sutherland, Andrews of Leith and Adamsons of Dunfermline), but in the end it led to a successful turnover of power. Simon was broadly derided by the parts of the nobility that had been supporting one branch or another of Clan Douglass - but history has been kinder, christening Simon "Simon the Wise" not long after his death in 108.
Prince Colin VII has gone down in history as "Colin The Fair".
The MacArthur dynasty only 64 years - although clans and septs aligned with MacArthur held the throne for nearly 400 more years - but they were among the most explosively dynamic years in Caledonian history. Colin VII only ruled for six years - he was 67 when crowned, and retired at 73. But the days of monarchs killing other monarchs (and, more commonly, their relatives and heirs) were over for nearly a millennium (until the Dynastic Crisis of 1024). The MacArthur accessession, and the political reforms necessary to accomplish it, led to Colin's son, Stuart IV, engineering The First Constitution, the dawn of the Caledonian constitutional monarchy.
The Douglass Concord, and the First Constitution, are often cited as key reasons Caledon has been able to prosper since the end of the Long Night.