Here is the full list of all 39 Opus Castle achievements.
Final Office Room
Achieve all achievements
See the pictures of the office
Collect the Gun
Find pin 3 of the key
Go to the entrance
Interact with 7 verifiable items
Drink until fall
Collect the invocation tape
Collect the pot of mugwort
Steal the jewels
Ending Room of Álvaro
See the photo of Alvaro's bedroom
Take a deep breath with the cigarette
Enter Alvaro's bedroom
Final Suit
See the photo of the suit
Enter the suite
Find pin 2 of the key
Check up the stairs
Ending Dinner room
Open the drawers
Get a drink
Eat a little
Enter the dinner room
Interact with 3 verifiable items
Find pin 1 of the key
See the photo of the hall
Collect the cassette player
Collect 3 items
Interact with the mirror
Find the base key
Play with the goat
Get run over
Use your cell phone flashlight
Access the company's app
Change the cell phone's wallpaper
Take a look around on the town
Try to run