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