Thelbane is the name given to the Realm which to all intents and purposes is the first 'Real' place that ever existed. When Cornelius the Great, and the other original beings, came from whichever place they preciously were, Thelbane is they place they settled, and where the first Logrus was built, anchoring 'Reality', and forming a permanent place, separate from the Abyss, where corporeal existence was possible.
The act of founding Thelbane, and building the Logrus was to all intents and purposes the end of the story as far as Cornelius was concerned - rule in Thelbane passed almost immediately to his son Swayville, with the title 'Keeper of the Logrus' going to Swayville's younger brother Suhuy.
Thelbane had its time of greatness, under King Swayville the Golden, but that time is now long past. The third son of Cornelius was Dworkin Barrimen, and he held radically different views about the nature of Reality - views which he was not willing see unrealised. As a result of his actions a new Realm called Amber came into being, populated by a family far stronger than the people of Thelbane, and peaceful coexistence was always a temporary thing. In the last war fought between Thelbane and Amber (called the Patternfalll war) Swayville and Suhuy both passed away.
The confusion that engulfed Thelbane in the time after the Patternfall war saw several brief occupations of the throne. For a short while Merlin, son of Dara Helgram, held the throne in a government strongly backed by House Helgram. However, when the Head of House resigned from his position of Prime Minister, and departed from Thelbane to begin the construction of his own Logrus in another place, Merlin's government eventually descended into civil war, before the eventual emergence of Mandor, son of Gramble Sawall, as the new King.
With the eventual emergence of Swayville's papers, obtained by Lauren Helgram and authenticated by her father Roland Helgram, it has been determined that Merlin was in fact the legal successor to Swayville at the time of his rule — a point which has been heavily emphasised by Dara in her campaigns to have Mandor declared a regicide. Swayvilles rules were:
In the only statement thus far issued on the matter, the High Justiciar of Thelbane has stated he accepts the validity of the evidence presented by the Swayville papers and thus campaigners for the return of Merlin are basically supporting a restoration of the Swayville succession, whereas supporters of Mandor are in effect supporting a new succession by conquest or usurpation.