The Kings' Stone

In the middle of the Great Hall, at the centre of the Court-of-All-Nations, there is a grey stone. Standing at mid-thigh on a tall man and around the same dimensions around as a generously-built beer barrel, but considerably less symmetrical, the top of the stone has been worn smooth and flat.
This is the Kings' Stone and is the reason for the existence of the Court-of-All-Nations. As Empires split into Kingdoms, and further fragmented, only to be re-combined in later dynasties, a number of ruling families laid claim to this stone as a key element of their coronation ceremony.
It did seem to have some power, for any monarch not crowned while seated on the King’s Stone lost their power, position, kingdom or even life within a year of their coronation. Others may have had short-lived reigns, but none so short or unhappy as those who had chosen a cushioned chair, rather than a seat of rock when receiving their crown.
In a rare moment of accord across the entire continent, the problem of the King’s Stone was raised, and in response, a citadel was built, as close as possible to the equidistant point between the ruling cities of all kingdoms at the time.
In the centuries since, while cities and thrones have moved, kingdoms and dynasties have risen and fallen, the Court-of-All-Nations has remained, untouched by conflict and the coronation of a new sovereign is accompanied by a month-long amnesty between all nations to allow safe travel for all who would attend.
This inevitably led to conversations, treaties, alliances and problems resolved over a table rather than a blood-sodden field and the Court-of-All-Nations now stands as the centre of diplomacy for the entire continent.
There has been a recent movement. Unofficial, yet unstoppable all the same to change the name of the stone. People do like accuracy in this world and the stone has seen the ascension of far more than Kings. The challenge is what to name it. Ruler Stone? It sounds like a mathematical tool. Monarch Stone? Are Dukes and Earls monarchs? For they have been deemed as worthy of the stone's regard as any other ruler over the eons. Most now simply refer to it as 'The Stone' and leave it at that.