Most of the information about The Interdiction Age can be found here.
Additionally, Varikin, a researcher from Luzeliot's Luminary Observatory, visited The Travail and delivered a document with information that, during The Interdiction Age, more than 30 worlds died.
One of the Old Heroes revealed that the Heroes of The Travail knew that The Interdiction was coming before it began. He passed away shortly after revealing that information.