There are 3 unique codex entries in the Game Rules section on Onderon. They are accessible to all players regardless of class or faction.
Amplifiers is obtained near a proximity map trigger.
Codex type: Game Rules | Faction: Both | Class: All
Associated Achievement: None
Set Bonus Items is obtained near a proximity map trigger.
Codex type: Game Rules | Faction: Both | Class: All
Associated Achievement: None
Tactical Items is obtained near a proximity map trigger.
Codex type: Game Rules | Faction: Both | Class: All
Associated Achievement: None