The Nayoman Invasion
The invasion of the Nayoman was in many ways was the defining moment at the beginning of the Era after the Light stopped, attracted by many things including the birth of spaceflight and the bursts of energy as Taltos ascended to the heaven this space faring race brought with them destruction and chaos to all worlds of the crucible.
The greatest armies of the Crucible could only stand against the Nayoman for a matter of days, and very quickly the peoples of the crucible were forced into hiding, captured or just outright massacred where they stood.