Here is the full list of all 13 Depths of Fear :: Knossos achievements.
Complete 15 'unknown' levels in a row
Complete 5 'unknown' levels in a row
Defeat the Minotaur
Defeat the Hydra
Defeat the Medusa
Defeat the Manticore
Defeat the Centaur
Defeat the Cerberus
Defeat the Griffin
Destroy 100 monsters
Level complete without being seen
Defeat the Satyr
Destroy 25 monsters