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