The Time of The Crossing chronicles are a collection of tales, myth, and history of the coming of the Blood of Saemon and their arrival on Helca (the the turmoil it caused). The basics that are commonly understood is that those who came were mostly human, fleeing a dying world that was beset by the Unholy Trio, and that the followers of the dark gods pursued them, eventually leading the evil gods to the world of Helca. The Time of the Crossing is understood to represent the start of The Modern Age – The Crossing Era.
The origins of the Blood of Saemon are from the setting of Greyhawk – End of Days.