There are 3 unique codex entries in the Achievement: PvP section on Ilum. They are all unobtainable.
Ilum: Captured an Objective is unobtainable.
Codex type: Achievement: PvP | Faction: Both | Class: All
Associated Achievement: None
Ilum: Captured the Zone is unobtainable.
Codex type: Achievement: PvP | Faction: Both | Class: All
Associated Achievement: None
Ilum: Killed Someone Using a Turret is unobtainable.
Codex type: Achievement: PvP | Faction: Both | Class: All
Associated Achievement: None