No missable achievements (plus 13 unknown)
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Level complete without being seen
Destroy 25 monsters
Destroy 100 monsters
Defeat the Satyr
Defeat the Cerberus
Defeat the Centaur
Defeat the Manticore
Defeat the Griffin
Defeat the Medusa
Defeat the Hydra
Defeat the Minotaur
Complete 5 'unknown' levels in a row
Complete 15 'unknown' levels in a row