There are 2 unique codex entries in the Achievement: Datacrons section on Makeb. They are accessible to all players regardless of class or faction.
Galactic History 88: The Unlikely Champion is obtained from interacting with the +10 Yellow Presence datacron.
Codex type: Achievement: Datacrons | Faction: Both | Class: All
Associated Achievement: Makeb Datacron Master
Galactic History 89: Capturing the Dread Masters | Coordinates: 79, 2557 | Location: Makeb: Nosnehm Mesa
Galactic History 89: Capturing the Dread Masters is obtained from interacting with the +10 Green Endurance datacron.
Codex type: Achievement: Datacrons | Faction: Both | Class: All
Associated Achievement: Makeb Datacron Master