Codex/Skel

The  codex entry is located within the Bestiary section of a player's codex once it has been unlocked.

Codex text
"Despite their diminutive stature, the vicious and intelligent skels are a potential wild card in the three-way war for Hoth. Skels hunt in packs, are capable of wielding primitive weapons and are biologically adapted to survival on Hoth’s frozen plains. Their bony claws are capable of burrowing through even the thickest snow and ice, allowing them to spring devastating surprise attacks.

Imperial war strategists dismiss the skels as a threat, but Republic soldiers are encouraged to report any mass gatherings of skels immediately. Long before the Republic, the Empire or the White Maw came to Hoth, the planet belonged to the skels–and these well-organized natives may decide to eliminate the unwelcome invaders."

- Star Wars: The Old Republic, codex entry

Entry details
Apparently this codex is Republic only (Need confirmation). You can get it during The Beast Lord mission by defeating Force Controlled Skel. Also available during Frostclaw mission by defeating Vicious Skel Pack Leader
 * {| cellpadding="0" cellspacing="0"

| Planet | width="12px" | | Hoth |- | Area | | Clabburn Tundra |- | Lore Object | |
 * }

Rewards

 * ? XP