Early on in the first act of Baldur’s Gate 3, the player can visit an abandoned temple of Selune (the goddess of the moon) that has been taken over by goblins. With a little exploration, you’ll come across a small room with a puzzle inside it – there are four circular plates on the floor of the room, with four symbols showing full moons, half moons, and new moons on each.
Solving this puzzle will give you access to the deepest reaches of the temple and serves as an entrance to the Underdark, a terribly dangerous area that you really shouldn’t explore until you’ve hit level four and gathered all the best equipment that the surface has to offer – lest you get ganked by a Bullette or some other nasty beastie.
Updated August 7, 2023 by Ryan Bamsey: With Baldur’s Gate 3’s launch, we’re learning more about the game with each passing day. We’ve given this guide a lick of paint to make sure it’s updated to the current version of the game.
How To Solve The Moon Door Puzzle
Before attempting the puzzle, the player should ungroup the other members of the party, as this will stop them from getting in the way when trying to manipulate the circles.
A clue to this puzzle is found in the Shattered Sanctum, in the room filled with Firewine Barrels and Smokepowder Barrels. There is a mural showing four phases of the moon in a diamond formation, with the full moon on the top, the new moon on the bottom, and half moons on the sides. This room is to the left of Priestess Gut’s room and can be accessed without antagonizing the traders by going through wooden platforms near the ceiling.
In order to solve this puzzle, located in the Defiled Temple, you’ll need to rotate the panels so that all of the new moons (the black circles) are moved to the bottom, which is the panel with the light shining on it.
The door to the Defiled Puzzle is located in Priestess Gut’s room. You will have to bypass an encounter with a guard on the way, or sneak past if you’re stealthy enough.
The full moons (white circles) need to be moved to the top panel, with the four half-moon icons placed at the four points furthest to the right and left. The best way to do this is to sort out the full moons first – once you have them in place, you shouldn’t need to rotate the top panel at all, just the lower panels.
Solving this puzzle will give you inspiration points and experience for every party member with the Sage background, such as Gale.
The image above shows you what the puzzle should look like. Only the circle at the bottom (nearest the entrance to the room) is lit, and all four new moons (the black ones) are within that circle. Once that is accomplished, the door to the Underdark will open.