Here is the full list of all 34 Eyes in the Dark achievements.
Kill 200 guardians.
Unlock the entire bookshelf.
Successfully complete Act IV.
Clear an entire zone without taking any damage.
Kill 50 guardians.
Complete a 9 zone run in under 45 minutes.
Finish a custom 9 zone run with at least 3 anomalies.
Complete a 9 zone run without using a single projectile.
Fully upgrade all 3 item categories.
Successfully complete Act III.
Complete a 9 zone run without upgrading a single weapon category.
Complete a 9 zone run without picking up a flashlight module and/or upgrade.
Complete a 9 zone run without picking up a projectile module and/or upgrade.
Complete a 9 zone run without picking up a gadget module and/or upgrade.
Complete a 9 zone run without equipping any items.
Scrap more than 50 items during a single run.
Successfully defeat Wormitor.
Successfully defeat Blobor.
Successfully defeat Hermitor.
Successfully complete Act II.
Have at least 1000 sparks in a single run.
Successfully defeat Mothor.
Successfully defeat Stingor.
Successfully defeat Arachnor & Snipor.
Kill a guardian without jumping.
Kill a guardian without using the slingshot.
Successfully complete Act I.
Successfully defeat Hiveor.
Successfully defeat Broodor.
Kill a guardian without using dodge.
Successfully defeat Insector.
Buy all 3 items offered in the shop.
Play the hidden tune in the Entrance Hall.
Complete the tutorial.