Chaos in the Stream
This event caused enough turbulence that scholars in Dullet and Dreadwood set the end of the Current Era at the date of the Purge. All dates prior to this became BCE (Before Current Era)
All magic below a certain level of power failed. Given the society’s (mostly human) reliance on magic, this caused a mass of deaths and uproar.
The fallout from this event several hundred years later would generate a stigma around magic that kept it from coming back into practice to any great extent.
Note – The elven kingdom’s were largely unaffected for several reasons, but mostly that they don’t use simple or weak magic in their everyday lives.