There are 4 unique codex entries in the Achievement: Datacrons section on Rishi. They are accessible to all players regardless of class or faction.
Galactic History 90: The Battle of Alderaan is obtained from interacting with the +10 Red Mastery datacron.
Codex type: Achievement: Datacrons | Faction: Both | Class: All
Associated Achievement: Rishi Datacron Master
Galactic History 91: The Syndicate Wars is obtained from interacting with the +10 Purple Mastery datacron.
Codex type: Achievement: Datacrons | Faction: Both | Class: All
Associated Achievement: Rishi Datacron Master
Galactic History 92: The Hydian Way is obtained from interacting with the +10 Orange Mastery datacron.
Codex type: Achievement: Datacrons | Faction: Both | Class: All
Associated Achievement: Rishi Datacron Master
Galactic History 93: The Mandalorian Schism is obtained from interacting with the +10 Blue Mastery datacron.
Codex type: Achievement: Datacrons | Faction: Both | Class: All
Associated Achievement: Rishi Datacron Master