It's not hard to find, a quick google search finds it, and The Dark Decent has a similar file, But A Machine For Pigs doesn't
It contains things that can be considered spoilers, and the passwords given in parts for completing the different endings
Super Secret file (The Dark Descent) | Amnesia Wiki | Fandom
The Super_Secret file is a .rar file located in the redist folder of Amnesia: The Dark Descent and is locked with a password only obtainable by getting all three endings of the game. After every ending, you will get a part of the password, and you must combine the letters and numbers in order to get the password.
Super Secret file (Rebirth) | Amnesia Wiki | Fandom
Like Amnesia: The Dark Descent, the .rar contains concept arts, development images, and even few scrapped materials for Rebirth
Post edited December 03, 2020 by UhuruNUru