Here is the full list of all 22 Obscurant achievements.
Disguise yourself for the first time.
Collect all disguises.
Name an enemy in the notebook.
Take notes in the notebook.
Bait an enemy into attacking another enemy.
Complete the Machine Wastes region.
Ride a zipline.
Complete the Kurtovsk region.
Gain entrance to the Kingdom.
Complete the Kingdom region.
Avoid chaos.
Reveal the truth.
Complete the Caelfos Opera House region.
Kill an enemy using the environment.
Complete the Templum Obscura region.
Witness the Second Obscurance.
Talk to an enemy.
Mimic four different types of enemies in one area.
Potato fritters, delicious.
Complete the Machine Wastes region with less than five minutes on your internal clock.
Complete the Kurtovsk region without overclocking.
Complete Zephyr's performance without missing a step.