There are 2 unique codex entries in the Achievement: Epic Enemies section on Hoth. They are accessible to all players regardless of class or faction.
Gargath is obtained from killing the world boss which wanders around the Gargath's Watch map section.
Codex type: Achievement: Epic Enemies | Faction: Both | Class: All
Associated Achievement: Gargathuan
Snowblind is obtained from killing the world boss which wanders around the Snowblind's Hunting Grounds map section.
Codex type: Achievement: Epic Enemies | Faction: Both | Class: All
Associated Achievement: Whiteout