Codex/Galactic History 81: The Battle of Telos Four

The Galactic History 81: The Battle of Telos Four 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:

The forces of the Sith Triumvirate had hunted the Jedi almost to extinction. The Jedi Exile, cut off from the Force, went in search of the remaining Jedi Masters and, perhaps, an explanation. But the Exile’s mentor, Kreia, had other plans–when the Exile finally gathered the Masters, Kreia slew them all.

As the Exile recovered from this encounter, Kreia deliberately enticed the terrible Darth Nihilus to the planet Telos Four. Nihilus prepared to devour all life on the planet, and Nihilus’s dreadnought, the Ravager, was met by the Republic Navy and Mandalorian forces.

During the battle, the Exile boarded the Ravager and faced Nihilus. Unable to devour the Exile as he had so many others, Nihilus was finally defeated. With Telos safe, the Exile pursued Kreia."