The Secrets of Loc Muinne

The Secrets of Loc Muinne is a side quest in The Witcher 2: Assassins of Kings, available in Chapter 3. Near the great tower in the middle of Loc Muinne, Geralt meets two alchemists who claim that the laboratory of Dearhenna, a long-dead but renowned sorcerer, lies hidden under the ruined city. They invite him to join an expedition in search of it.

The other members of the expedition turn out to be the Nilfgaardian mages Cynthia and Adalbert. Geralt can either attack them on the spot, ending the quest early, or join them. If he joins, the group passes through sewers full of necrophages, solves riddles posed by Dearhenna’s guardians, fights a band of rival Redanian treasure hunters and gets past a golem guarding the laboratory. Both alchemists, Gaspar and Farid, die along the way to the sorcerer’s traps.

Inside the laboratory Cynthia reveals a hidden artifact built by Dearhenna, a machine that uses an emotional bond to create a magical link with another person over long distances. How the expedition ends depends on Geralt’s dealings with the two mages. The quest fails if Geralt advances the main story too far before entering the cellars.

Walkthrough

Speak with the alchemists near the central tower of Loc Muinne, then meet the rest of the expedition in the cellar under the tower.
Choose whether to fight Cynthia and Adalbert immediately or join them.
If you join, follow the sewers toward the laboratory and kill all the necrophages.
Locate the laboratory entrance and let Cynthia dispel the illusion hiding the door.
Examine the guardian eye above the door and answer its riddle correctly.
Enter the fresco room and defeat the Redanians.
Wait for Cynthia to reveal the second guardian and speak to it.
Solve the fresco riddle by standing on the correct pressure plate and placing two companions on the other correct plates.
Enter the laboratory and try to trick the golem; if you fail, defeat the golems instead.
Search the laboratory together with Cynthia and Adalbert and wait for Cynthia’s spell to reveal its contents.
Examine Dearhenna’s artifact and deal with the mages’ reaction: let them leave with it, fight Adalbert with Cynthia’s help, or fight both mages.
Use the artifact if you have the chance.

Quest Consequences & Choices

The outcome depends on how Geralt handles the Nilfgaardian mages:

Peaceful ending: Geralt lets Cynthia and Adalbert take the artifact. Before leaving, Cynthia shares information about Geralt’s own past, recovering memories he had lost to amnesia.
Cynthia sides with Geralt: Adalbert forbids Geralt from touching the artifact and attacks him, and Cynthia fights on the witcher’s side. After Adalbert dies, Cynthia allows Geralt a single use of the artifact, then the two part on friendly terms as she leaves through a portal with the machine.
Both mages hostile: If Geralt defeats both of them after they turn on him at the artifact, he can use the machine himself to listen in on several people before its power runs out after three connections.
Both mages killed early: Killing Cynthia and Adalbert without a mage to remove the illusions leaves Geralt unable to find the artifact, and the quest fails.