Murtagh enters the dark chamber beyond the guarded tunnel door and finds a war room with a map of Alagaësia, scrolls, and another locked door leading deeper into the catacombs. After hiding the sleeping guard inside and relocking the outer door, Murtagh resists the temptation to search Captain Wren’s plans because time is limited.

The next door is made of ancient Môgren wood and carved with Dwarvish runes, with a depression matching the bear mask from Wren’s study. Rather than risk returning for the mask, Murtagh tries to mold a wooden shelf into the lock with magic, but the spell splits the door loudly, ensuring the break-in will be discovered.

Beyond it, Murtagh finds a magical workroom built among the ribs of a dragon, possibly Morzan’s dragon. The room contains alchemical tools, potions, books, and gems; Murtagh takes a dictionary of the ancient language and a yellow diamond charged with energy. The chamber’s contents deepen his fear that Wren, or another hidden magician, is using the place for dangerous arcane purposes connected to werecat younglings.

At a dragon-bone door set with energy-filled jewels, Murtagh suspects a trap. Instead of forcing it, he drains the jewels’ power into the yellow diamond, then into a werelight when the diamond overheats and nearly explodes. The risky maneuver leaves him shaken but succeeds; the door opens without triggering an alarm.

Murtagh enters an underground garden filled with medicinal, poisonous, visionary, and unfamiliar magical plants, including a tentacled pitcher plant that devours a frog and a strange blue-black egg in a crystal case. Uneasy and wishing for better guidance, he moves to a final granite door, finds no magic or consciousness beyond it, and begins to worry that Carabel may have manipulated him.

Behind the stone door, Murtagh discovers a bare cell containing only a tiny sky-blue blanket that smells of fear and a chalk outline of a doorway on the back wall. The evidence convinces him that Silna, or another child, was imprisoned there, triggering memories of his and Thorn’s captivity under Galbatorix. Grief turns to rage, but as Murtagh turns to leave, a brindled, clawed creature launches from the corner and attacks his neck and shoulders.