Balthazar’s Experiment – Baldur’s Gate 3

Baldur's Gate III Game Guides

The Gale companion and The Wizard of Waterdeep questline continues in Baldur’s Gate III (BG3) with Balthazar’s Experiment. Which, even if you managed to help him back in act 1 with the magical items, Gale will admit that his condition is worsening. Here’s how to take the next steps to helping our wizard companion with his quest. This quest begins during act 2


The Wizard of Waterdeep (First Companion Quest)

Meet Elminster

With Gale in the party. Head through the mountain pass. You will meet a weary traveller who turns out to be Gale’s mentor. He will do a wonderful fussy old man routine until you agree to let him rest at your camp.

After a rest in your camp Elminster will tell you he is here on Mystra’s behalf. It seems Gale’s goddess will give him a way to stop his affliction for now so that he can use it to eliminate the absolute. However, the way to eliminate the absolute will kill Gale.

Meeting Elminster in Balthazar's Experiment
Elminster Gale’s Mentor

Balthazar’s Experiment BEGINS

In the Moonrise towers, be sure to have Gale in the party as you solve the bookshelf puzzle and enter a hidden room. You’ll see a magic circle on the desk that you can use to make The Shadow Lantern that will not only help with the curse but help you wield it. Making it with the dead pixie and lantern in the room will give you the spell to summon a shadow wraith.

However, the magic used to make it is clearly dark and will not be approved by Gale’s goddess. If you would like to help him gain her favour, you will need to destroy the magic circle. In exchange for missing that shadow wraith you will gain Mystra’s favour and Gale, or whoever erased the circle will gain advantage on all constitution saving throws to keep their concentration spells up. Generally a very useful reward for a wizard.


In the Mind Flayer Colony, during the battle with Kethric Thorm the leaders of the absolute will summon the elder brain. Gale will quickly see this as his chance to fulfil his goddess’ wishes.

You can talk him out of it as this is an end to the game in only Act II. Gale’s sacrifice will destroy Moonrise Towers and the elder brain. You will get an ending but as the narrator says, “Not the one destiny has in store for you.”

Find Another Way

If you talk Gale out of sacrificing himself and continue with the game you can continue with his companion quest by visiting the Sorcerous Sundries in the Lower City. This will be to research the crown on the elder brain’s head that seemed to be controlling it.

Speak to Tolna Tome-Monger at the back of the shop to learn about the rare tomes they have here. Use a Deception, Intimidation or Persuasion check to get her to drop the info that the way into their vault is through her office, she won’t let you in but you’ll know where to go.

Break into The Vault

The next step in the Balthazar’s Experiment quest is to head up the stairs and go to the left. The door to the office will be open but you will be seen as trespassing as soon as you enter. Make use of any extra stealth spells you can to sneak in. Take the key from the desk then head over to the bookshelf and click the clasped book. It will open a portal to the vault.


Obviously in a Vault there will be many things to look out for but what we want for this quest is the Annals of Karsus. To find it head through a door to the south. The next door you come across will be locked. Pick it open. In the next room there will be three doors. Two are to vaults and one is to start the puzzles to unlock them. To unlock Karsus’ vault you will need to head through the Silverhand door, then the Adjuration door, followed then by the silver door.

Be aware of traps as you go and when you are through the silver door, pull the lever in the room.

Once you have done that you can head back out, via any other door and be returned to the start of the maze. The door of Karsus’s vault will be open but there will be a trap in front of the door. Teleport or jump over it to enter the vault and pick up the Annals of Karsus.

Gale reads the book and gets the idea of taking the stones and crown and reforging it. It does sound a little like madness considering everything it has caused so far so feel free to agree or disagree.

Mystra Calls

The Goddess Mystra

Later you will come across Elminster again and he tells you that Mystra knows that Gale has not done as told. He says that she would like to see Gale at her shrine in the Stormshore Tabernacle to speak with her.

Head to said shrine with Gale and after a small pep talk, he’ll go to talk to her. She explains her point of view, explains how she has temporarily cured Gale of his affliction and bids that he returns the crown to her when we have taken it from the brain.

Whether you do this or something else, will be a choice you make at the end of the game.

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