There are 2 unique codex entries in the Achievement: Epic Enemies section on Ilum. They are accessible to all players regardless of class or faction.
Gravak'k is obtained from killing Gravak'k. It is only available during the Relics of the Gree event.
Codex type: Achievement: Epic Enemies | Faction: Both | Class: All
Associated Achievement: Advanced: Whomping the Wampa
Surgok'k is obtained from killing Surgok'k. It is only available during the Relics of the Gree event.
Codex type: Achievement: Epic Enemies | Faction: Both | Class: All
Associated Achievement: Advanced: Slugging the Slug