Here is the full list of all 38 Darkness Within 2: The Dark Lineage achievements.
Underline Arkhamend in the letter that Loath Nolder left.
Find the attic trapdoor in the cottage.
Acquire the key to the door in the first dream.
Finish the first dream sequence.
Persuade Henry to sell the book.
Find a metallic box with a copy of Necronomicon and a statue of Cthulhu.
Solve the recollections of the past book puzzle.
Find the stone building in the forest glade.
Solve the jigsaw puzzle in the old stone building.
Prepare the mixture for the dangerous insects.
Open the small trapdoor which holds the key to the underground galleries of the old stone building.
Find the protective suit.
Solve the disc puzzle in the elevator.
Find the secret room in the underground galleries of the old stone building.
Summon Wolfgang Schneider from beyond
Find the Homunculus experiment.
Retrieve the whereabouts of the mansion named The Gate.
Enter the Mansion cellar.
Finish the childhood dream sequence in the Loried mansion.
Find the concealed compartment in the floor of Nathanael’s room.
Find Monkey’s Paw Secret.
Discover your father’s coffin in the tomb.
Open the Secret Kitchen Room.
Unravel the Native Bust Secret.
Speak with Loath Nolder.
Combine elements to get a secret Ankh.
Find the Lovecraft book in the Worm’s feast.
Discover Henry's dead wife.
Retrieve the second part of the key, from the nursing home.
Retrieve the third part of the key, from grandma’s room.
Find the Dead Reporter Secret.
Find the book of Darkness Within 1 along with a Lovecraft book in the mansion.
Find a symbolic picture of the Zoetrope development team on the table.
Solve the steam puzzle in the elevator.
Use the last puzzle piece on the door beneath the well.
Choose the good ending.
Doom and Gloom
It is good to have enough flashlights.