Baldur’s Gate 3 Guide: Find and Open the Necromancy of Thay Book

Baldur’s Gate 3 players looking to unlock the “Nekromantie von Thay” spellbook will need more than curiosity—they’ll have to move through a multi-stage dungeon route, handle a talking magical mirror, steal a key component from under a dangerous spider nest, and then complete a late-game portal puzzle to reach the final page. Here’s how to do the whole chain without getting lost, plus what you risk if you try to read (or destroy) the book immediately.

Finding the book: Act 1 cellar route, talking mirror, and a rusted key

The process begins in Act 1 at the Ruined Village. Go to the Apothecary building—the second structure on the left—and check the counter where you’ll find a book tied to the quest “Durchsuche den Keller.” Behind that counter is the cellar entrance leading to the underground challenge.

Inside, you’ll need a rusted key. It’s located in a western-most room of the laboratory, stored in a rack. From there, look for a set of three wooden crates near a large cabinet wall. After passing a Perception check, you’ll discover a lever that opens the way to the next hidden room. You can grab and toss the crates aside to reach the lever; when activated, the cabinet wall shifts and the passage becomes accessible.

You’ll also run into enemies in this section. After they’re dealt with, you reach an ornate mirror. Starting a conversation with the speaking magical mirror is what allows you to proceed. The mirror can be fooled using a specific response sequence: first, “Yes, a companion! A companion of your master.” Next, “Szass Tam is evil and abominable.” Then, “Balsam is used for wound care.” Finally, “I would look for a spell that frees me from this worm.” Once the mirror is satisfied, it lets you pass and you’ll enter the next room.

Inside, a research note on a table continues the quest, and you’ll then use the rusted key to open a closed gate. The Necromancy of Thay book is behind that gate. Before grabbing it, the game expects you to deal with multiple traps—so it’s strongly implied you should clear hazards first rather than rushing in.

At this point, the book can be read and opened, but the next steps depend on a key item you’ll need before the full secret is accessible.

Decoding the Necromancy of Thay: the Dark Amethyst, the reading outcomes, and class-based options

To follow the dark path and open the book properly, you’ll need a Dark Amethyst. This item is obtained in the Ruined Village’s “Whispering Depths,” reached by traveling to the well in the village and entering that area. Expect combat against Phasenspinnen (phase spiders), then push toward the nest of the Matriarch in the far west.

Players can either stealth in—an Invisibility potion is specifically suggested—or fight the Matriarch directly. The glowing violet Dark Amethyst is found under the Matriarch’s nest beside a broken column, and you’ll need to press “Left-Alt” to interact and collect it.

With the amethyst in hand, you can read the Necromancy of Thay again. From there, multiple outcomes are possible, and the game uses Wisdom checks that scale by page.

If you successfully read it yourself, you’ll face three Wisdom checks with increasing difficulty—10, 15, and 20. Passing all of them grants the achievement “Verborgenes Wissen.” It provides a +1 bonus to all Wisdom saving throws and skill checks, and it also unlocks the 3rd-level necromancy spell “Speak with Dead.” However, even with the successful reading, the final page isn’t immediately available—meaning the quest continues and will take you to later content.

If you fail the Wisdom checks, the game applies curses that differ based on how many saves you miss. After the first failure you suffer “Whispers of Insanity,” and after the second you suffer “Unheilvolles Wissen” (meaning ominous/ill-fated knowledge). Both curses can be removed with the spell “Remove Curse.”

The reading difficulty can also be adjusted depending on your class. Bards can roll Performance checks with DCs of 5, 10, and 15. Sorcerers? (Not listed.) Instead, the guidance given is: Wizards can roll Intelligence checks for the first attempt at DC 5, while later pages still use the pre-set Wisdom checks. Warlocks get to roll a Charisma check for the first attempt at DC 5, while subsequent pages still use the Wisdom checks. Wizards?—again, the specified class option is for Wizards and the first roll at DC 5 via Intelligence.

Clerics have a special reduced requirement on the third page if their deity aligns with the Dark/Evil side (examples provided include Talos, Gruumsh, and Lolth). For that page, the Wisdom check is reduced to DC 10 instead of 20. Shadowheart is also included here as a Cleric of Shar.

There are also companion-specific and team-play options. Gale can be given the Necromancy of Thay after you’ve collected the Dark Amethyst; importantly, this option isn’t available if you open the book before offering it. Astarion can be given the book after it’s opened, earning his approval and advancing his unique story. But you can only give it to one of these story characters.

If you choose to destroy the book instead, the method described is dealing holy damage to it. The guide warns against this approach: triggering that route can lead to three dangerous shadow enemies with high resilience, and without a strong party you’re likely to die quickly. The consequences for companions are also noted—Astarion won’t like the destruction, while Karlach, Lae’zel, and Wyll are more likely to be receptive.

Finally, you can also put off the decision and leave the book unresolved, with the choice to be handled later in the game.

One major spoiler note: The steps required to reach the final page involve content revealed much later in the campaign.

To read the last page, you’ll need to reach Baldur’s Gate and then go to the area tied to “Zauberhafte Kleinigkeiten,” which is part of the “Zauberer von Tiefwasser” quest chain for Gale. In that location, find the librarian’s office, then interact with the book clutched in a shelf. This interaction opens a dark portal that teleports you to a spell vault.

An alternative route to that spell vault exists too: press one of the large buttons in Lorroakan’s tower labeled “Tresorraum,” which also provides access.

Once inside the vault, explore the area until you reach a puzzle room. From there, you go through doors in a specific order: Silberhand, Beschwörung, Wunsch. Be mindful of traps throughout the process. After that, use the lever in the final room and return to the first room; the Elminster vault should then be accessible.

Inside the Elminster vault you’ll find the Tharchiate Codex, which is required to read the last page of the Necromancy of Thay. The final Wisdom check is demanding: you must roll a 20. If you succeed, the reward is a powerful spell that allows you to summon ghouls.

If you’re still deciding whether to bring Gale or Astarion to your party, the guidance also points players toward a companion team-building guide so you can plan your group before committing to the necromancy chain.