The two hidden Tenebris Somnia endings each need a brand-new playthrough, and both stay locked until SOLVE ET COAGULA and MAGNUM OPUS are already recorded. One of them takes two minutes, and the other takes a whole run of deliberately wrong solutions.

RENUNTIATIO: the walk-out ending

RENUNTIATIO (Ending #4, hidden, reached by 12.8% of players) is the shortest route in the game.

  1. Start a new game.
  2. Use the Apartment Key on the building's glass front entrance door in the ground-floor lobby.
  3. Julia walks out, the credits roll within minutes, and the run is over before the first puzzle.

No fight, no puzzle and no Aurifer are needed. Do this one before the other hidden ending, because it costs a couple of minutes. The other three endings are in the endings guide.

VIVUS EX MORTIBUS: three Iron Crosses

VIVUS EX MORTIBUS (Ending #3, hidden, 7.3%) is the rarest ending in the game, and it needs three Iron Crosses.

  1. Start a new game and take the Bible from the table in the ground-floor lobby.
  2. Carry the Bible to three puzzles, taking the alternative solution at each one first. Every alternative solve spawns a fight, and winning that fight pays one Iron Cross.
  3. Order matters, because solving a puzzle the normal way destroys the Bible.

The three puzzles, in the order you have to do them:

  1. Floor 2 apartment, TV room. Before you solve the TV remote puzzle, use the Bible, start at the Mars (male) symbol and make six counterclockwise circuits around the symbol plates. The room turns red and enemies appear. Beat them for Iron Cross #1. This one has to come first, because the normal TV solve loses the Bible.
  2. Floor 1 projector room padlock. Before you use the phone's code, use the Bible and enter 6666. Beat the enemies in the altered red room for Iron Cross #2.
  3. Floor 0, green-door Cinematography classroom. Before you go through the Copper Key door, use the Bible, attach the yellow RCA cable to the camera and cycle through the camera feeds until enemies appear. Beat them in the red version of the classroom for Iron Cross #3.

Where the Bible, the Copper Key and the camera are is in the item locations list.

Where the three crosses go

The crosses are placed at the blue door on Floor 3, to the left of the elevator. Insert the three Iron Crosses into the wall on the right of that door and step through it. The route continues to the street and into the church, where the route ends in a fight against the possessed woman alongside the priest John. That fight is in the final boss guide.

Before you start the Tenebris Somnia secret ending run

  • The bar bottle pitch, the elevator colour order and the fly-tile route still reroll every playthrough, so solve those by method again rather than by memory.
  • The Bible is destroyed by the normal solution of each of the three puzzles, so do the alternative version first in every case and never let the Bible be spent elsewhere.