Full list of all 28 Dark Bestiary achievements.
The base game contains 25 achievements, and there are 2 DLC packs containing 3 achievements.
Complete Nightmare V.
Reach level 40.
Complete Nightmare IV.
Complete Nightmare III.
Complete Nightmare II.
Reach level 30.
Complete Nightmare I.
Reach level 20.
Kill Amaroq without killing any of the wolves he calls.
Reach level 10.
Kill the Fairy Dragon while not being affected by Euphoria Breath.
Kill the Broodmother while not allowing any spider spawns.
Don't kill Fluffy.
Complete Nightmare VI.
Complete Nightmare VII.
Complete Nightmare VIII.
Complete 10 treasure maps.
Complete Nightmare IX.
Complete Nightmare X.
Reach level 50.
Reach level 60.
Reach level 70.
Reach level 80.
Reach level 90.
Reach level 100.
Complete campaign.
Complete "Tower of Ascension" scenario.
Complete "Dream" game mode.