Lacuna Fight — Good Ending Final Boss (SOLVE ET COAGULA)

Lacuna is the Good ending final boss of Tenebris Somnia. You only reach her by completing the Aurifer Knife chain (Lapis Fictus → Melanosis → Virdis → Aurifer) and sprinting through the apartment to Séptimo Arte without killing any Relicta ghosts with the Aurifer. The phase tactics, the Relicta-sprint branch, and the Acrophobia missable hook all live on this page; the four-ending overview is on endings and the Aurifer forge chain is on knife weapon.

Lacuna only appears if you pick the Good ending branch. Concretely:

1. Reach the Desiderium dream layer and run the full Lapis Fictus → Melanosis → Virdis → Aurifer forge chain — see knife weapon.
2. After the Aurifer cutscene, do not kill any Relicta ghosts with the Aurifer. Sprinting past them (or detouring around the rooms without swinging) keeps the Good branch active.
3. Use the Lead Key dropped from the TV after the cutscene to open the symbol door; walk north through every door to the locked Hotel door; the Aurifer Knife scene plays here.
4. Sprint through the Hotel doors back to the Studio Lobby, exit to the hallway, take the furthest-right door to the staircase, climb to Floor 3, enter the apartment hallway, far left go through the door with the water puddle, then left in the street to the Séptimo Arte building with the Relicta ghosts and enter the building.

Killing even one Relicta with the Aurifer flips the branch to the Bad ending and you will instead face Hermes — see Hermes fight.

Lacuna's Phase 1 is a high-mobility melee pattern built around a scream-jump-land grab. She teleports short distances, screeches, jumps, and attempts to grab you when she lands. The safe loop is:

1. Stay at mid-range between her melee and her full jump.
2. Dodge sideways when she teleports — she always telegraphs the destination by facing the landing spot a moment before the blink.
3. Punish once after each scream-jump-land if you sidestepped cleanly; her recovery animation is long enough for one swing.
4. Never stand still through the jump. A stationary player inside her landing radius gets grabbed and the cutscene kill triggers — that grab is also the trigger for the Acrophobia missable, see below.
5. After the grab animation finishes (whether you die or barely break free), the phase resets the same pattern at a slightly faster cadence.

Phase 1 ends when her health bar drops to roughly a third. There is no Phase 2 on this branch — solving Phase 1 triggers the SOLVE ET COAGULA cutscene.

The Acrophobia achievement pops when Lacuna's grab kills you in Phase 1. It only registers if you actually stand still through the scream-jump-land and let the grab connect. Easiest setup:

1. Enter the Séptimo Arte arena with the Good branch active.
2. Wait through the first dodge cycle so Lacuna enters her scream animation.
3. Stop pressing dodge / move as she jumps and lands on your tile.
4. Let the grab animation run to completion; you die; the achievement text appears next to the SOLVE ET COAGULA credits.

Acrophobia is Hidden on Steam until unlock — only completionists see it in the public list, and the global percentage is not displayed. It is the rarest Good-branch missable and requires you to plan a Phase-1 die deliberately. If you accidentally die earlier in the fight from a stray hit, the achievement still counts because the grab is what triggered the kill.

If you want SOLVE ET COAGULA without Acrophobia, keep dodging sideways and do not stand still through the jump. Reload from before the Séptimo Arte entry to retry the other path.

• Survive Phase 1 cleanly → credits roll → SOLVE ET COAGULA achievement pops (visible on Steam, ~12.1% global unlock).
• Die to Lacuna's Phase 1 grab → Acrophobia + SOLVE ET COAGULA both pop in the same ending cutscene.

Either way, Lacuna is the only Good-branch final boss. There is no Phase 2 to plan around. Plan the Acrophobia die in a separate run from any other endings to avoid invalidating SOLVE ET COAGULA later.

• Endings — branch selection and the four-ending overview.
• Knife weapon — the Aurifer Knife chain that gates reaching Lacuna.
• Walkthrough — the Aurifer-to-Séptimo Arte sprint route.
• Achievements — full Steam percentages for both Acrophobia and SOLVE ET COAGULA context.