Baldur's Gate 3 Underdark: Guide to Levels, Map, and Spectator Boss

Baldur's Gate 3 does not have a seasonal system. The latest major update was "Patch 8" (released April 15, 2025), and Hotfixes (correction patches) have been continuously released since. The latest Japanese patch for the PS5 version, "Patch 1.800.801," was distributed on March 27, 2026. This article's information is based on these versions.

The "Underdark," a vast and eerily lit subterranean world. This area, arguably Act 1's greatest challenge, is filled with dangerous monsters and valuable treasures. Recommended for characters at levels 4-5, this region holds rewards that will greatly aid your adventure, such as the unique weapon "Phalange of Arl" and the "Adamantine Forge," where you can craft some of the most powerful armor. This article thoroughly covers all aspects of Underdark exploration, from every entry route to strategies for defeating the formidable "Spectator" and the locations of hidden items and equipment.

4 Entry Routes to the Underdark

There isn't just one path to the Underdark. There are primarily four routes, each leading to a different location. While you can eventually explore the entire area regardless of your chosen route, your starting point will affect ease of movement in the early stages.

1. From the Defiled Temple (Goblin Camp)
   This is the most common route, easily accessible through the story progression. Solving a puzzle in the room behind Goblin Priestess Gut or activating a hidden lever opens the way to the Underdark. This route leads directly to the former Selûnite Outpost, offering good access to the powerful weapon "Phalange of Arl" and the "Spectator" boss, both detailed later.
2. From the Whispering Depths (Blighted Village)
   Descend into the well in the Blighted Village and jump into the large hole in the area where the Phase Spider Matriarch, boss of the Whispering Depths, resided. This route has a significant vertical drop, so your entire party must have the "Feather Fall" spell active, or they will die from fall damage. With proper preparation, you can land near the center of the Underdark.
3. From the Zhentarim Hideout Elevator
   Gain access to the "Zhentarim Hideout" by establishing a cooperative relationship with the merchants in Waukeen's Rest. Using the elevator at its deepest point will take you to the northwestern Underdark. This exit is far from other routes, providing a varied exploration experience.
4. From Auntie Ethel's Teahouse Basement
   Progress through "Auntie Ethel's" quest and teleport from the mushroom circle beyond the hidden passage behind the fireplace in the teahouse's basement. This route connects to a somewhat isolated area in the southwest, requiring a bit of travel to reach the Myconid Colony.

Recommended Exploration Route and Key Area Explanations

For exploring the Underdark, it's efficient to first head for the friendly Myconid Colony located in the center and use it as a base to venture into other areas. We recommend beginning serious exploration once your characters gain a class level to 5, as fighter-type classes acquire "Extra Attack" and spellcasters gain level 3 spells (like Fireball), significantly boosting your combat power.

"Myconid Colony": Your Exploration Hub

The "Myconid Colony," located in the center of the Underdark (near coordinates X:100, Y:-100), is a safe hub with merchants and quest-givers. Speaking with Sovereign Spaw, the colony's ruler, initiates one of the main quests, "Defeat the Duergar Intruders," which serves as a guiding objective for exploring the entire Underdark.

Additionally, the colony is home to another exiled sovereign, Glut. You can choose to aid him, defeat the Duergar, and then betray Spaw to install Glut as the new ruler. This choice not only alters the colony's fate but also provides an opportunity for unique rewards.

Selûnite Outpost Ruins and the Formidable "Spectator"

Upon entering the Underdark from the Defiled Temple, you will first reach this area. Here, important items, equipment, and a very challenging boss await.

• Hidden Item/Equipment: Phalange of Arl
  On the west side of the outpost ruins, a glowing longsword impaled in the cliff is the "Phalange of Arl" (near coordinates X:116 Y:-191). To pull it out, you must succeed on a [Strength] or [Religion] check. This sword possesses a unique ability: when the wielder performs a "Song" or "Shout" action, it grants a powerful buff to nearby allies. For front-line classes with supportive abilities / spells / class features, such as Bards, Paladins, and Clerics, this weapon offers exceptional performance for Act 1.

Once you acquire the Phalange of Arl, proceeding further west (near coordinates X:134, Y:-233) will initiate a battle with the "Spectator" boss without warning. This monster is a lesser species of the race commonly known as "Beholder."

The Spectator is a formidable foe with 118 Hit Points (HP) and AC 14, unleashing various condition-inflicting attacks such as Petrifying Ray, Confusion Ray, and Fear Ray. When combat begins, the Spectator frees petrified Drow in its vicinity and uses them as its allies. However, these charmed Drow, once they take any damage, break free from the charm and begin attacking the Spectator as your allies. Effectively utilizing this gameplay technique is key to victory. If you keep the first Drow leader freed, "Dawne," alive, you will receive additional dialogue and rewards after the battle.

Fungus Forest and the "Find the Mushroom Picker" Quest

The "Fungus Forest" (also known as the "Dreadful Fungus Forest") is where you'll go for the "Find the Mushroom Picker" quest, assigned by Derryth in the Myconid Colony. This area is extremely dangerous due to prevalent poisonous spores that damage you just by walking. Spores can be temporarily removed with torches or fire spells/arrows, but be careful not to involve Baelen, the rescue target, in explosions, as he will also take damage.

To safely rescue Baelen, it's effective to either teleport quickly near him using the "Misty Step" spell or a Spell Scroll, or to throw the pouch at his feet to him. After the rescue, you'll receive valuable items and equipment as a reward, and you can also obtain the quest item "Noblestalk" deeper in the area. This mushroom is crucial for a later event to restore the memory of an important character, so be sure to acquire it.

To the Deepest Reaches: Sussur Tree and Adamantine Forge

As you progress through the Underdark, you will reach even more critical locations.

The Sussur Tree

On the west side of the Underdark stands the "Sussur Tree," which emits an aura that suppresses magic. While powerful monsters like Hook Horrors patrol the vicinity, you can obtain "Sussur Bark" at the tree's base. This is a vital material required for the "Finish the Masterwork Weapon" quest, which can be accepted in the Blighted Village on the surface.

Final Objective: The Adamantine Forge

The "Adamantine Forge," the ultimate objective of this area, is located in the deepest part of "Grymforge," which you reach by taking a boat from the southern beach of the Underdark. Here, by combining "Mithral Ore," which can be mined nearby, with "Moulds" hidden within the area, you can craft up to two incredibly powerful Adamantine items.

Among the craftable equipment, the heavy armor "Adamantine Splint Armour" and the medium armor "Adamantine Scale Mail" possess exceptional properties: they reduce all damage taken by the wearer and completely negate critical hits. Equipping these on your front-line characters will dramatically improve their survivability.

However, activating the forge requires pouring lava, and in the process, a battle with the gigantic boss "Grym," the forge's guardian, will ensue. Grym is an extremely tough opponent that is very difficult to defeat without utilizing specific mechanics, so prepare thoroughly before challenging him.

Summary

The Underdark is a highlight of Act 1, a vast area that tests a player's tactics and exploration abilities. Key points for success are as follows:

• Recommended to gain a class level to 5: It becomes significantly easier if you challenge it after acquiring "Extra Attack" and level 3 spells.
• Use the Myconid Colony as a base: Utilize it as a quest hub and a guide for your exploration.
• Understand the Spectator battle's mechanics: Freeing the charmed Drow and turning them into allies is key to victory.
• Always craft Adamantine equipment: The armor that negates critical hits, in particular, will provide immeasurable benefits in future adventures.

While the dangers are great, wonderful items, equipment, and experiences commensurate with the risk await you. Use this article as a guide to successfully explore the mysterious and threatening subterranean world.