No I was thinking of Freedon Nadd. Most of what I've read about him says that he awakened Naga Sadow from stasis on Yavin 4 and then later killed him after he learned the secrets of the Sith from him. I don't think I'd ever heard about him learning from a holocron of King Adas. In fact, since King Adas was a Sith ruler long before the arrival of the Dark Jedi Exiles who became the Dark Lords of the Sith, how would he even have had a holocron? I thought they were Jedi teaching equipment.
Research indicates that King Adas learned of Holocron technology from the Rakata after the Sith repelled a Rakata invasion. Remember that this is the research of a Sith researcher. I will do my own research to back-up or supplant these claims.
Freedon Nadd destroyed Naga Sadow's spirit after he had assumed that he had learned everything from him.
Edit: King Adas was taught how to create Holocrons when visitors from the Infinite Empire arrived to Korriban. He built his own, but then had to fight off the subsequent Rakata invasion. The Holocron was lost until Nadd found it. After thousands of years, the Holocron fell into the hands of the Dark Lady Lumiya.