The Collapse was a cataclysmic event that happened long before the events of Chaos Before Apocalypse, in the 18th Century. Nobody really knows how it began; some say one of the kingdoms had launched a mega-weapon, some say it was an unusually powerful earthquake that affected things worldwide, some believe it was an imperfect, magic spell by some unknown mage trying to end the world that failed in their goal. But while its speculated origins differ, the end result was the same: globally, cities were levelled, buildings fell to ruin, and countless people died.
Though the first few years were marked with chaos, grief, and confusion; all hope was not lost. There was bloodshed, yes, but most survivors of the post-apocalypse did band together, forming communities & keeping their cultures alive as best they could. Ten years after The Collapse, this all culminated to a group of mages creating the Singing Spheres; magical orbs that helped society rebuild & recover even faster.
Though many old scars remain; abandoned castles & old ruins marring the landscape not far from many modern cities; the world keeps turning, and humanity moves on.