Travel through the Underdark

Travel through the Underdark is a sub-quest of  Travel to Moonrise Towers in Act One of Baldur's Gate 3. It can be acquired after speaking to either Halsin or Minthara after resolving  Save the Refugees by siding with either the tieflings or the goblins.

Objectives

Objectives and journal entries may vary pending story decisions and outcomes.

Travel through the Temple of Selûne.

• Halsin told us that there is a way to Moonrise Towers that leads through the Underdark. Tunnels beneath the temple of Selûne will lead us there.
• We learned that the best way to get to Moonrise Towers is through the Underdark. Tunnels beneath the temple of Selûne will lead us there.

Find the secret entrance to the Underdark.

• We found the old temple of Selûne. The entrance to the Underdark must be here somewhere.

Unlock the secret entrance to the Underdark.

• A room in the old temple of Selûne contains a secret entrance to the Underdark. Through it, we can reach Moonrise Towers.

Go through the secret entrance.

• We unlocked a secret door in the old temple of Selûne. It leads to the Underdark.

Explore the Underdark.

• The Underdark is a twisted labyrinth of tunnels and ruins. To find the path to Moonrise Towers, we'll need to explore.

Reach Moonrise Towers through Grymforge.

• We learned that the Absolute sent agents to Grymforge. There must be a route connecting Grymforge and Moonrise Towers.
• We discovered a lift in Grymforge that can bring us closer to Moonrise Towers. However, we were warned of a darkness that plagues the surface.
• Reach Moonrise Towers through Grymforge.

Quest Complete

• We used the lift in Grymforge and arrived in the shadow-cursed lands.
• We decided to take the mountain pass. This road should lead us to Moonrise Towers.

Walkthrough

NOTE: It is not necessary to choose between exploring the Underdark and the Mountain Pass. Both can be visited before going to the Shadow-Cursed Lands.

If meeting with Halsin as part of  Rescue the Druid Halsin, he explains that he cannot heal the party, but that he has been studying the Absolute cult's activities and knows that they are sending people en-masse to Moonrise Towers. He suggests that the party head there to seek answers. During  Save the Refugees, if the Druid Grove was protected, Halsin speaks with the party after the night of celebration. He explains that there are two paths to Moonrise Towers - one through the Underdark and one overland through the Mountain Pass. The area around Moonrise Towers is known as the Shadow-Cursed Lands, and has a dangerous curse that can drive people mad. Halsin recommends the Underdark route, as it means travelling over less of the areas infected by the shadow curse.

If the party side with Minthara, she tells them only about the Rosymorn Monastery Trail, providing a Spider's Lyre so that the party can summon one of her minions to cross the Shadow-Cursed Lands overland. She states that the party must go to Moonrise Towers to find their pace in the Absolute's Grand Design. However, the party is still free to go to the Underdark instead.

Finding an Entrance

There are several ways to enter the Underdark. Only one of these paths needs to be pursued to enter the Underdark.

Defiled Temple

The correct combination for the Defiled Temple puzzle.

One path to the Underdark is through the Shattered Sanctum in the Goblin Camp. The entrance can be accessed through Priestess Gut's chambers, but is guarded by her ogre servant Polma. If talking to Gut about a cure for the tadpole infection and then following her to her chambers, she says that a special cleansing potion must be taken first. However, an Arcana check reveals that this is a Potion of Sleep. If she is called out on this, or if the party member in question is resistant to sleeping potions (i.e. being a Drow, Elf or Half-Elf), she and several nearby goblins become hostile.

However, if the potion is taken (and works), she chains up the party member and says she intends for them to become her pet squid.

It is possible to break free with either an Acrobatics or a Strength check, but if nothing is done at all, Korrilla appears from a portal to assassinate both Gut and her Ogre guard. Then she disappears after a brief conversation, warning the party to be more careful.

Once in the Defiled Temple, there is a puzzle blocking the way forward. There are four overlapping circles. The goal is to get the black circles into the southernmost circle. Follow the combination to unlock the door:

• South
• East
• South
• North
• East

Alternatively it is possible to find a locked lever on the right side of the door near the stairs upon a successful perception check. It can be then unlocked using lockpicks.

The party must venture through the now-unlocked door and climb down the ladder to enter a Selûnite Outpost. The gate forward is closed and guarded by moon magic, but can be opened by using ranged attacks on the Moonstone held by the Selûne Statue. Another option is to exit out of the broken window on the western wall of the outpost.

Whispering Depths

Use Featherfall to jump down the chasm.

There are two ways to enter the Whispering Depths. One way is to enter the blacksmith's basement north of the Blighted Village Waypoint; this is also the same basement where  Finish the Masterwork Weapon is completed. One of the northern walls is cracked and can be destroyed with force damage, which leads to the Whispering Depths. The other way is to investigate the well at X: 23 Y: 400 north of the Waypoint. The party must choose "[INVESTIGATION] Peer into the well" and then climb the bucket rope ladder down into the well to arrive at the cave.

The chasm to the Underdark is by the Spider Matriarch's nest at X: -558 Y: -360. In order to jump safely from the chasm, the party must use  Feather Fall or a similar spell. Otherwise, the party's bodies are shattered upon impact from the massive height.

Zhentarim Basement

The Zhentarim Basement can be reached through a barn west of Waukeen's Rest, at the shabby door at X: -113 Y: 613. The party members are automatically aware of the Zhentarim Hideout depending on if Rugan and Olly were encountered as part of  Find the Missing Shipment - either by speaking with Rugan or by asking his corpse questions with  Speak with Dead. If sparing Rugan's life, he shares the location of the hideout along with the password needed to enter. With a successful perception check, the party can notice Salazon, crouching behind some shelves. Reciting the password 'Little serpent, long shadow' lets him stand down immediately and provide the key to a wardrobe that leads into the hideout. If not having the password, there are other options to get past Salazon:

• Read his mind.
• [BERSERKER] [INTIMIDATION] Do NOT make me angry! (DC 15 )
• [BARBARIAN] [INTIMIDATION] Careful. You won't kill me, but you will make me mad. (DC 15)
• [PERSUASION] Just calm down - I'm not here to fight. (DC 15)
• [ROGUE] [PERSUASION] This is all pretty crude, as traps go - you'll probably kill us both. (DC 15 )
• [SORCERER] [PERSUASION] I am magic. Cast that spell - you'll only hurt yourself. (DC 15 )
• [DRACONIC SORCERER] [PERSUASION] Fire is in my blood. Do it. Let's see who survives. (DC 15)
• [WILD MAGIC] [PERSUASION] Every spell I cast could be my last. You think I fear death? (DC 15)
• [WIZARD] [PERSUASION] That spell, in close quarters? You're going to hurt yourself. (DC 15 )

The illusory wall leads to an elevator that descends to the Underdark.

Succeeding to make Salazon stand down allows the Zhentarim to be dealt with peacefully. The party must follow his instructions to go down the hatch and through the wardrobe to enter the Zhentarim Basement. Once inside, following the path forward and climbing up the ladders leads to where Zarys can be encountered. Then party then must move north and cross the bridge. A man named Karad has a mechanical key and guards the way further. Slightly north of Karad is an illusory wall at X: 268 Y: -189 which can be detected with a Perception check. The party can move through the wall and either use Karad's key on the Elevator Winch or lockpick it. After this it is possible to use the elevator platform to descend to the Underdark.

The Hag's Basement

Another illusory door blocks the way to the Underdark

The party must enter Auntie Ethel's teahouse in the Sunlit Wetlands at X: -47 Y: 266 and use Ethel's illusory fireplace to enter into the Overgrown Tunnel. The first hurdle is a door of vines. Attempting to use it causes it to telepathically share its story with the party to warn them from proceeding further. An Arcana check reveals that the door is an illusion and can simply be walked through. Otherwise, passing a DC 10 Persuasion check causes it to share its secrets.

Through the door are four servants of Ethel's - Mask of Terror, Mask of Vengeance, Mask of Regret, and Mask of Servitude. They become hostile upon detecting the party. On the table next to the door are Whispering Masks. If worn it prevents the Hag Servants from becoming hostile. However, while Auntie Ethel is alive, the wearer of this mask must make a Wisdom saving throw every turn. If failed, they become a Hag's Pawn (controlled by Auntie Ethel) and attack the party; if all party members equip the masks and fail their saving throws, a Game Over screen appears. If all of the unaffected party members run away from combat (i.e. back to the Tea House), leaving no one to attack, the remaining mask-affected party members are able to unequip the mask after making a wisdom saving throw.

Past the Hag Servants is a waterfall and a winding path filled with noxious fumes and explosive traps. On this path, there is a door to the north at X: -354 Y: 577 which can only be passed while at least one party member is wearing a Whispering Mask. The party must pass through the door and interact with the Mushroom Circle to enter the Underdark.

Getting to Grymforge

Once arriving in the Underdark, the party must make their way forward to find a way up into the Shadow-Cursed Lands. There are many helpful quests in the Underdark, including a main quest to attempt to remove the tadpole -  Help Omeluum Investigate the Parasite - but only two quests in particular directly assist in moving further into the Underdark.

The first of these quests is  Defeat the Duergar Intruders, which allows the party to kill the duergar at the Decrepit Village X: 11 Y: -195 and steal their boat to get into Grymforge. The second quest is  Find the Missing Boots, which involves working with the duergar to track down a missing gnome who stole some boots, and then being charged to deliver the boots to Grymforge. The party can also attempt to sneak past the duergar and sneakily access the boat without doing either quest.

Once in Grymforge, the party is tasked with many different objectives, including freeing a True Soul drow named Nere as part of  Free True Soul Nere. However, the party can almost immediately ascend to the Shaadow-Cursed Lands upon entering Grymforge. East of the Grymforge Waypoint is an elevator at X: -603 Y: 382. Upon interacting with the Wrought-Iron Gate to the elevator the party is stopped by Magmar. Magmar asks the party if they have one of Nere's Moonlanterns and explains that they risk succumbing to the shadow curse without one. The party can tell him that they are not concerned about the curse and the proceed forward to use the elevator to the Shaadow-Cursed Lands. If the duergar are gone or dead, then a gnome named Skickpit initiates the same conversation.

Consequences

Entering the Shadow-Cursed Lands is considered the "point of no return" for Act One and is the official start of Act Two. As such, using the elevator in Grymforge means that several quests automatically update. Before entering the elevator, complete all desired quests.

Notes

• Both the Mountain Pass and the Underdark have unique quests and loot. For the most complete playthrough, it is recommended that the party explores the Mountain Pass, Underdark, and Grymforge before going to the Shadow-Cursed Lands.