The Necromancy of Thay is a cursed magical tome in Baldur’s Gate 3 and a major necromantic grimoire in Forgotten Realms lore, filled with knowledge about death, undeath, and twisted resurrection.

What Does the Necromancy of Thay Do?

In Baldur’s Gate 3 (Gameplay Effects)

In BG3 , the Necromancy of Thay is a unique quest item tied to “Search the Cellar,” “Unlock the Ancient Tome,” and “Destroy the Ancient Tome.”

You find it in the Blighted Village, in the hidden lab beneath the trapped cellar with the talking mirror and undead.

Once you open and start reading it, the book has several concrete effects on the character who interacts with it:

  • Grants a permanent Speak with Dead spell
    • Turning at least one page permanently unlocks Speak with Dead for the reader.
* It becomes a ritual you can cast without a spell slot, which is extremely useful for gathering information from corpses throughout the game.
  • Bestows Forbidden Knowledge
    • If you turn three pages , whether you succeed or fail their checks, the reader gains the Forbidden Knowledge passive and the Forbidden Knowledge tag.
* This tag can influence certain dialogue and reflects that your character has delved into dangerous Thayan secrets.
  • Ongoing risk–reward reading
    • Each page involves checks that can damage or mentally overwhelm the reader if failed, reflecting the corrupting nature of the text.
* Players often debate whether it is safer to read deeply for maximum benefits or stop early to avoid long‑term consequences.
  • Quest state behavior
    • If you close the book before reading three pages, the “Search the Cellar” quest remains incomplete, and you can come back to the book later.
* Destroying or giving up the tome resolves the storyline differently but forfeits its mechanical benefits.

Overall, in BG3 , what the Necromancy of Thay “does” is:

  • Give you a free, at‑will Speak with Dead ritual.
  • Potentially grant Forbidden Knowledge and unique story flavor.
  • Expose your character to necromantic danger and corruption for the sake of power.

In Forgotten Realms Lore

In broader D&D/FR lore, The Necromancy of Thay is described as a powerful arcanabula (a magical tome) containing advanced necromantic theory.

It is tied to the Red Wizards of Thay and liches like Szass Tam, who spearheaded Thay’s undead legions and vast necromantic projects.

The book’s themes and purposes include:

  • Secrets of undeath and lichdom
    • The tome details methods of reanimation, soul anchoring, and techniques for sustaining undeath.
* It explores things like partitioned phylacteries and complex soul‑binding, pushing necromancy past “simple” raising of skeletons.
  • Twisted resurrection magic
    • The Necromancy of Thay focuses on warping resurrection , trapping souls between the mortal world and the Fugue Plane.
* The design goal is to turn resurrection into a weapon: the spell can suspend a soul in a limbo state while necromantic effects take hold.
  • Corrupting, mind‑warping knowledge
    • The book is intentionally constructed so that those who begin its deepest rites but cannot complete them have their minds overwhelmed.
* Its “glyph chains” react to the reader’s competence, reshaping themselves and pressing insights into the mind like “iron filings behind the eyes.”
  • A vehicle for Thayan necromantic doctrine
    • The text is explicitly meant to spread the accumulated necromantic knowledge of Szass Tam and the zulkirs out into the world.
* It acts as a kind of communion channel to the land of the dead, tying Thayan necromancy to the broader metaphysics of the Realms.

In other words, lore‑wise , the Necromancy of Thay is both:

  • A manual on advanced necromancy, undeath, and soul manipulation.
  • A dangerous artifact engineered to propagate Thayan necromantic power while breaking the minds of the unworthy.

Mini FAQ: Common Player Questions

“Should I read or destroy it in BG3?”

  • Read it if you want long‑term mechanical power (permanent Speak with Dead) and don’t mind the role‑play of dabbling in something very dark.
  • Destroy or give it up if you role‑play a character who rejects necromancy or you want to avoid the theme of being tainted by Thayan magic.

“Is it only a BG3 thing?”

No. BG3 uses the Necromancy of Thay as a prominent artifact, but it is grounded in established Forgotten Realms lore about Thay’s necromantic tradition and Szass Tam’s works.

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.