There are 4 bestiary entries on Voss. All four are required for the Beastmaster of Voss achievement.
A Cyberbeasts codex entry location obtained from a Cyber Vorantikus.
Codex type: Bestiary
Codex location: Voss: The Gormak Lands: Cyber-Beast Training Grounds
Codex coordinates: 829, 1510
Faction: Both
Class: Bounty Hunter - Imperial Agent - Jedi Consular - Jedi Knight - Sith Inquisitor - Sith Warrior - Smuggler - Trooper
Associated Achievement: Beastmaster of Voss
A Mawvorr codex entry location obtained from a Thalak Mawvorr.
Codex type: Bestiary
Codex location: Voss: The Nightmare Lands
Codex coordinates: 709, 402
Faction: Both
Class: Bounty Hunter - Imperial Agent - Jedi Consular - Jedi Knight - Sith Inquisitor - Sith Warrior - Smuggler - Trooper
Associated Achievement: Beastmaster of Voss
A Shaclaw codex entry location obtained from a Corrupted Shaclaw Treesplitter.
Codex type: Bestiary
Codex location: Voss: The Nightmare Lands
Codex coordinates: 1193, -314
Faction: Both
Class: Bounty Hunter - Imperial Agent - Jedi Consular - Jedi Knight - Sith Inquisitor - Sith Warrior - Smuggler - Trooper
Associated Achievement: Beastmaster of Voss
A Vorantikus codex entry location obtained from a Vorantikus Patriarch.
Codex type: Bestiary
Codex location: Voss: The Pelath-Ri Marches
Codex coordinates: -425, -1183
Faction: Both
Class: Bounty Hunter - Imperial Agent - Jedi Consular - Jedi Knight - Sith Inquisitor - Sith Warrior - Smuggler - Trooper
Associated Achievement: Beastmaster of Voss