Here is the full list of all 12 The Forgotten Ones achievements.
Discover the ritual room
Beaten the game.
Schienzel is forever dead.
Found the book of darkness.
Got the meat cleaver.
You killed the tourists.
You spared the tourists.
You did what was necessary.
Something is burning...
Use an healthkit at low health.
Got the SVT-40.
Got the FG-42.