In the Amnesia: The Dark Descent expansion Justine, Justine Florbelle is a disembodied voice who taunts the player character through phonographs set up around the dungeon that she finds herself in. While Justine's motives are initially unknown, the player can collect diary entries and listen to more phonograph recordings to learn about who she is and what horrors she has conducted in the dungeon.
Apparently mentally unsound as a child, she was educated by her father (who seemed to be a scientist of some sort) in an unusual and experimental way, through the systematic characterization of thoughts and feelings into slides with certain characters imprinted on them. This upbringing, however, backfires, causing her to become emotionally detached from reality and leading to "disturbing actions."
Some time later she begins exploring the dungeon (which is the basement to her family's castles) and discovers the scientific work her father had been doing. She kills him down there and begins re-equipping it to suit her new, twisted needs. Soon after, she enters into a love rectangle with three suitors, Alois, Basile, and Malo. One by one, she brings them down to her dungeon, locks them in, and tortures, mutilates, and maims them until they've become inhuman monsters.
As the player proceeds through the game, it becomes clear that the player character is actually Justine. She has drugged herself for fun and philosophy and is making herself run through the horror dungeon of her own creation. The expansion ends with Justine's successful escape from the dungeon, and she returns to the manor proper to be greeted by a servant, who is making preparations for the evening's guests.
A secret alternate ending can also be unlocked that slightly changes Justine's conversation with the servant to reference the game Portal. Before making her final escape from the dungeon, Justine can find a secret letter from A.S. Inc. in Boston in which the company talks about their latest creation: the Span-space Device. The letter includes a slip to be filled out and mailed back. When Justine encounters her servant at the end of the game, she requests that the return letter be sent, though she admits that the response is far out of date. She simply wants them to know that she's "still alive." This alternate ending plays into the Potato Sack ARG that several games participated in the lead-up to Portal 2.