The origin and history of Orithia is a hotly contested subject. There are dozens of versions of the story and hundreds of variations within each and the ‘correct’ version often depends on who one asks with each major nation and religion having a slightly different adaptation.
When the Cathedral of the Great Wheel was constructed in Salamonis, the priests of each faith faced many difficult decisions regarding the uniting of over a dozen major religions and had to cross-reference the myths, legends, stories and histories of each into a final form which allowed peaceful integration and transition from one faith to another. The very act of working together in such a fundamental way it is said created the binding force which persists to this day.
Here is the official version of Orithia’s history according to Salamon.
This timeline is widely held to be correct, and many stories exist which develop the detailed history of a particular region or people which fit into this tale and indeed, expand upon it for example this account of Northlands History or the detailed account of Kondar’s rise to power.