"I am Darth Atra, Dark Lord and founder of the New Sith Order."
-The Gatekeeper of Darth Atra's Holocron
Sometime before his death, Darth Atra constructed a holocron. The gatekeeper was a mirror image of Atra in his prime, which would have been during the Second Confederate War. It is speculate by scholars that this holocron was initially created during that same war, and updated periodically through his life. Inside the holocron were techniques that could be used by those wishing to become a New Sith. It is believed that many of Revan's teachings are included in the holocron.
In 1,000 NE, the holocron was in Darth Void's possession, and had been updated sometime after the Dark Lord's death. Void speculated that Darth Novus had updated the holocron after he had slayed Darth Atra 21 NE.