The Nephlim Purge was the systematic eradication of all Nephilim conducted by the Angels, Demons, and Humans in a combined effort. It was executed after The First Void Insurrection, when fear of the powers of the Nephilim were at their greatest due to the actions of the Void Avatar. Even though many Nephilim assisted in the war, and made great efforts to fight against Void, the other races deemed them too dangerous to live, and so set about eliminating them. This was also due to the fact that it was prophesized that a Second Void Insurrection would occur, and that another Void Avatar would be responsible, and so the three primary races also hoped to prevent this from coming true as well.
The Nephilim Purge resulted in the near extinction of the Nephilim race. Only a handful of Nephilim managed to survive and go into hiding. It is due to this event that there are now only three remaining Nephilim in the modern day, one of which is the next Void Avatar, even though so much effort was made to prevent it.