Here is the full list of all 19 Sword of the Slayer achievements.
Finish the game without any companions.
Finish the game with both companions.
Finish the game ruled by the sword.
Finish the game in service to Demorgon.
Finish the game in service to Ramsen and the nobles.
Finish the game in service to Mag.
Finish the game in service to the gods.
Finish the game and continue the hunt.
Finish the game ruling Targus Adur.
Defeat at least one non-spider monster.
Defeat at least three non-spider monsters.
Defeat at least six non-spider monsters.
Receive a boon from the gods.
Utilize a boon from the gods.
Utilize a boon from the gods to defeat Demorgon.
Return the gods to Targus Adur.
Finish the game without recourse to the gods.
Successfully kill the Great Wyrm.
Successfully free the Great Wyrm.