Codex/Galactic History 49: Exar Kun

The Galactic History 49: Exar Kun codex entry is located within the Achievements:Datacrons section of a player's codex once it has been unlocked.

Codex entry
"This datacron holds unheard of power and knowledge collected by an ancient race. You access its power and discover writings which are clearly only one small piece of a massive galactic history:

When the Jedi teach of the dangers of pride and overreach, they often speak of Exar Kun. A promising Jedi who trained on Dantooine, Exar Kun was known for his talent and his temper. He was intensely curious about all matters of the Force, and disagreed with his Master over the dangers of the dark side. Exar Kun believed he was strong enough to study the dark side without being corrupted by it.

Denied access to dark side teachings, however, Exar Kun left the Jedi in disgust. When he heard the Jedi had sealed the Sith Lord Freedon Nadd’s sarcophagus away on the jungle moon of Dxun, he went to Dxun to seek the tomb.

Breaking through the tomb’s seals, Exar Kun was confronted by the spirit of Freedon Nadd. Impressed by his power, Nadd told Exar Kun to journey to the Sith holy world of Korriban."