This is a walkthrough for the Investigate the Selûnite Resistance sidequest in Baldur's Gate 3. Read on to learn how to unlock the quest, where to find the hidden meeting area in Reithwin Mason's Guild, and the rewards you'll get from finishing the quest!

Side Quest Details

Journal Entry
Investigate the Mason's Guild The Mason's Guild seems to have been the centre of Selûnite resistance in the area. We should seek it out and investigate further.
Recommended Level	Level 6
Rewards	・Helmet of Arcane Acuity ・Moonrise Tower Prison Stash ・Random Scrolls and Potions ・Infernal Iron
Starting Location
Last Light Inn in the Shadow Cursed Lands
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How to Start Investigate the Selûnite Resistance

Read Haldfred's Note in the Last Light Inn Basement

To start the sidequest, you'll need to read Haldfred's Note in the hidden Selûnite Altar located in the basement of the Last Light Inn.

How to Get to the Last Light Inn Basement

Investigate the Selûnite Resistance Walkthrough

	Investigate the Selûnite Resistance
1	Get the Tower-Shaped Key from Mattis
2	Head Southwest from the Last Light Inn
3	Head Down the Ornate Wooden Hatch
4	Open the Keyholed Herald
5	Enter the Hidden Meeting Area
6	Defeat the Shadows
7	Read Mason's Log

Get the Tower-Shaped Key from Mattis

If you helped the Tiefling Refugees in the Emerald Grove, speak to Mattis who is in the main hall of the Last Light Inn and he will mention that Mol gave him a Dusty Key.

You can Persuade or Buy the key for 2000 Gold, which you can further bring down to 1000 Gold. Regardless of your choice, the Dusty Key becomes the Tower-Shaped Key.

Head Southwest from the Last Light Inn

You can reach the Reithwin Mason's Guild by following the path southwest from the Last Light Inn and through the makeshift bridge that brings you to the Reithwin Town Waypoint.

Requires Moonlantern of Pixie's Blessing

The area where the Reithwin Mason's Guild is surrounded by shadow that even the Blessing of Selûne can't protect against.

You'll need full protection, which you can get by obtaining the Moonlantern from Kar'niss and freeing the pixie to get the Pixie's Blessing*.

Seek Protection from the Shadow Curse

Head Down the Ornate Wooden Hatch

Once inside the Reithwin Mason's Guild, go to the western side of main area and climb down the Ornate Wooden Hatch.

Open the Keyholed Herald

Once inside, head to the western side of the room to trigger a Perception Check that will reveal the Keyholed Herald.

Of you got the Tower-Shaped Key from Mattis, simply interact with the Keyholed Herald to reveal the hidden passageway. Otherwise, you may also lockpick the Keyholed Herald to open it.

Enter the Hidden Meeting Area

Follow the passageway south and pass through the doors to enter the hidden Selûnite Meeting Area. Before progressing further, make sure to take a Short Rest or Long Rest as there are enemies you'll need to defeat.

Note: There is a reinforced treasure chest in the hallway leading to the meeting area that you need to disarm and unlock, but the chest is empty so you can just ignore it.

Defeat the Shadows

Head inside the room and you'll be attacked by five Shadows and a Wraith, with the latter emitting an Aura of Oblivion that extinguishes nearby light sources, which will cause the other shadows to disappear in areas with no light.

Prioritize killing the Wraith so that you can use your Torch, Light, Produce Flame, and Dancing Lights spells to illuminate the shadows and make them easier to track.

Note: Volo's Ersatz Eye grants you permanent See Invisibility, which will make it easier to track down the Wraith and Shadows.

How to Get Volo's Ersatz Eye

Read Mason's Log

Once the Wraith and Shadows are defeated, read Mason's Log on the stone dining table to learn more about Ketheric Thorm to complete the sidequest.

Investigate the Selûnite Resistance Rewards

Helmet of Arcane Acuity

You can find a Reinforced Chest in the altar area of the hidden meeting room that contains a Helmet of Arcane Acuity.

This chest requires you to disarm the trap twice to unlock it safely.

Moonrise Towers Prison Stash

Head to the western side of the hidden meeting area and inspect the Moonrise Towers Diagram on the small table. This will unlock a map Hidden Stash icon on your map that directs you to Moonrise Towers.

The hidden stash is located in the cave area leading to the hidden dock where Wulbren and the Tieflings will escape when you help them break out from Moonrise Towers Prison and contains a random amount of gold and arrows.

Rescue the Tieflings (Shadow-Cursed Lands)

Random Scrolls and Potions

Near the table where you find the Moonrise Towers Diagram, pass by the wall for a Perception Check that will reveal a button. Press the button to open a hidden wine cellar and loot the two heavy chests that contain random scrolls and potions.

Infernal Iron

You can find Infernal Iron on a table on the eastern side of Reithwin Mason's Guild.

Note: The Infernal Iron is located in the open area where you find the Ornate Wooden Hatch and not in the hidden area beneath the Mason's Guild.

All Infernal Iron Locations

Lore and Backstory

Reading Mason's Log reveals some lore and backstory regarding Ketheric Thorm, particularly that there is a hidden Sharran Temple underneath the Reithwin Mason's Guild.

This is in fact the Gauntlet of Shar, which is accessible through the Thorm Mausoleum, and is a small hint as to where Ketheric's immortality stems from.

How to Beat the Gauntlet of Shar

Baldur's Gate 3 Related Guides

List of All Side Quests

Prologue Side Quests

All Prologue Side Quests
How to Free the Intellect Devourer	How to Free Shadowheart

Act 1 Side Quests

Druid's Grove Quests

Druid Grove Quests
How to Steal the Sacred Idol	Should You Save The Goblin Sazza?	How to Avoid Tiefling Pickpockets
Save the Refugees	How to Save Nadira	How to Save Mirkon
How to Save the First Druid Halsin	How to Open the Stone Slab	Request Help from Nettie
How to Investigate and Expose Kagha	Save Arabella	-

The Risen Road Quests

The Risen Road Quests
Find the Missing Shipment	How to Rescue the Grand Duke
Rescue the Trapped Man	How to Free Oskar Fevras

Blighted Village Quests

Blighted Village Quests
How to Beat the Goblins: Blighted Village	How to Open the Necromancy of Thay	How to Recruit the Ogres
How to Finish the Masterwork Weapon	That Barn: Avoid Killing Buthir	Rescue the Gnome and Stop the Windmill

Goblin Camp Quests

Goblin Camp Quests
How to Get Volo's Ersatz Eye	Defiled Temple Puzzle
Find the Nightsong	Ask the Goblin Priestess for Help

Nautiloid Crash Region Quests

Nautiloid Crash Region Quests
Dank Crypt Guide	The Dying Mind Flayer	Auntie Ethel Quest Guide
How to Get Owlbear Cub	Spiderling Nest Guide-	How to Open the Selunite Chest
How to Get Scratch	Should You Heal Pandirna	Underground Passage Guide

Underdark Quests

Underdark Quests
Arcane Tower Guide	Defeat the Duergar Intruders	Save the Grymforge Gnomes
Find the Adamantine Forge	Deliver Nere's Head	How to Find the Mushroom Picker
How to Cure the Poisoned Gnome	Help the Cursed Monk	Omeluum Location

Mountain Pass Quests

Mountain Pass Quests
Steal a Githyanki Egg	How to Beat Gremishkas	How to Access Guardian of Faith Room
Dawnmaster Puzzle Guide	Where to Find the Githyanki Creche	-

This section is currently under construction. Check back later for updates!

Act 2 Side Quests

Last Light Inn Quests

Last Light Inn Quests
Seek Protection from the Shadow Curse	Rescue the Tieflings	Rescue Wulbren
How to Lift the Shadow Curse: Where to Find Thaniel	Find Zevlor	Help He Who Was
Investigate the Selûnite Resistance	-	-

Gauntlet of Shar Quests

Gauntlet of Shar Quests
Gauntlet of Shar: All Trials and Umbral Gems	Kill Raphael's Old Enemy

Mind Flayer Colony Quests

Mind Flayer Colony Quests
How to Solve the Necrotic Laboratory

Act 3 Side Quests

Rivington Quests

Rivington Quests
Investigate the Suspicious Toys	Solve the Open Hand Temple Murders	Find the Missing Letters
How to Get to Wyrm's Rock Fortress	How to Find Dribbles the Clown	-

Lower City Quests

Lower City Quests
How to Get to the House of Hope	How to Get to Cazador's Palace	Rescue Orin's Victim
Aid the Underduke	How to Get to the House of Grief	Investigate the Murders