Mind Flayer Tunnels – Baldur’s Gate II

This guide will walk you through the Mind Flayer Tunnels in the Underdark in Chapter 5 of Baldur’s Gate II. This area’s code in the game files is AR2402.

Overview

When you enter this tunnel system (at Exit A), you’ll immediately get captured by mind flayers and sent to a prison (#1). After you’ve been there for a short while, an ogre will show up and inform you that you’re now required to “pay for your stay.” He’ll then send you to the arena (#4), where you’ll be pitted against three umber hulks (worth 12,000 xp total). After winning the bout, you’ll receive five Potions of Extra Healing, and you’ll be sent back to your cell.

At this point, the door connecting your cell to an adjacent cell (#2) will no longer be locked, and you’ll be able to talk to Simyaz and his githyanki companions. They’ll tell you that their ship was capsized and they were captured while tracking down a Silver Blade that had been stolen from them — a story that should sound familiar if you worked with Saemon Havarian while escaping from Spellhold.

Right after your conversation, Simyaz and his party will get called away for their own fight in the arena. When they return, they’ll suggest working together to escape from the mind flayers. Simyaz will tell you that he and his companions can distract the mind flayers while you clear a way to the exit.

The next time you’re called into the arena (#4), it’ll be your party versus the githyanki party versus a kuo-toan war party. The githyanki will uphold their part of the bargain. They’ll start trading spells with the mind flayer spectators while you deal with the kuo-toan party (which is worth over 5000 xp).

After the battle, you’ll finally be able to explore the tunnels. You’ll need to do two things to escape:

• Open the security doors (#7) that are blocking the way to the exit (Exit A). To do this, you’ll need “a powerful mind or godly strength.” That is, you’ll either need to find a mind flayer to open the doors for you, or you’ll need to switch to your Slayer form and do it yourself. The latter option is the easiest, but it’ll cost you two Reputation points.
  
  To get a mind flayer to open the doors, you’ll need to go to the serum room (#5) and pick up some Illithid Serum from one of the vats there. The serum will allow you to wake up the slaves in the preparation room (#6), and use the machine in the back of the room to create up to four Control Circlets. The Control Circlets in turn will allow you to charm a mind flayer and send it into the security room (#7), where it will automatically open the doors (and then turn hostile). Mind flayers will spawn in the serum room every couple of minutes, so you should always have one available.
  
  When you open the security doors, Simyaz and his friends will show up, and they’ll tell you that they can now leave thanks to their “wings of will.” But you won’t be able to leave yet. You’ll have to complete one more step (see below). However, for completing this step, each character in your party will earn 25,000 xp.

• Kill the Master Brain to unlock the exit (Exit A). To reach the Master Brain, you’ll have to fight your way through numerous mind flayers (worth 9000 xp), ulitharids (worth 19,000 xp), and umber hulks (worth 4000 xp). To make these battles easier, you should head straight for the birthing pods (#8), where you’ll be able to create Brine Potions, which will protect you from psionic attacks.
  
  You’ll find the Master Brain in the control room (#12). It’ll have a mind flayer, an ulitharid, and an umber hulk guarding it — but it won’t notice you until you attack it, so take out its guardians first. When you eventually attack the Master Brain, two things will happen: the door to the control room will close and lock, and the Master Brain will summon a pair of brain golems (worth 10,000 xp each) to attack you. If you kill the golems, then the Master Brain will just summon more, so focus on the Brain first and then deal with the golems. You’ll only be able to damage the golems with magical crushing weapons.
  
  When you kill the Master Brain, you’ll earn 10,000 xp for its death, and each character in your party will also earn 40,000 xp. When you loot the Master Brain’s corpse, you’ll find gems (including Diamonds and King’s Tears) and 540 gp. You’ll also automatically loot its Elder Brain Blood, which you might need for Matron Mother Ardulace’s noble blood quest in Ust Natha. Finally, killing the Master Brain will unlock the exit from the tunnels (Exit A), which will allow you to escape.

1 – Your Cell

2 – Githyanki Cell

3 – Prison

You’ll encounter your ogre jailer here, and you’ll earn 10,000 for killing him. After the battle, you’ll find the Hilt of the Equalizer (needed by Cromwell in the Docks District to craft The Equalizer) on a table in the chamber.

4 – Gladiatorial Fighting Pit

5 – Serum Room

Inside this room, you’ll find the Illithid Serum needed for the preparation room to the south (#6). Every couple of minutes, a mind flayer (worth 9000 xp) will gate into the room. You can kill them for xp, but realize that it’s a good idea to keep one alive.

6 – Preparation Room

You’ll find several unconscious slaves, including a slave leader, in this room. You can wake them up by adding Illithid Serum (from #5) to the machines keeping them medicated. After killing the Master Brain (#12) and clearing the way to the exit (Exit A), you’ll run into the slaves on your way out, and they’ll thank you for your help. This will earn you 45,000 xp and a point of Reputation.

After waking up the slaves, the machine in the back of the room will allow you to craft four Control Circlets, which can charm mind flayers.

7 – First Security Room

To open the sealed doors in this room, you’ll either need to find a mind flayer to open them for you, or switch to your Slayer form and open them yourself. See the Overview text above for more information about how to do this. On the northern side of the room inside a piece of artwork, you’ll find Methild’s Harp.

8 – Illithid Birthing Pods

You’ll find eight illithid birthing pods here. Each one will allow you to create a Brine Potion, which will protect you against psionic attacks.

9 – Second Security Room

When you enter this room, you’ll get attacked by three mind flayers, three ulitharids, and two umber hulks. This is a good place to use a Brine Potion or two (from #8). You’ll earn 92,000 xp total for defeating the enemies.

The northern door from this room is another security door, just like the two you had to deal with in the first security room (#7). It can be opened in the same way.

10 – Solitary Confinement

In the three isolation chambers here, you’ll encounter an insane dwarf warrior, a kuo-toan priest, and an umber hulk. You’ll earn about 8000 xp for defeating them, and you’ll find a Ring of Fire Control on the dwarf’s corpse.

11 – Secret Room

In this room, you’ll encounter two mind flayers, an ulitharid, and an umber hulk. You’ll earn 42,000 xp for defeating them. When you loot the containers in the room, you’ll find a Staff of Command.

12 – Control Room

Exits

• A) Exit to the Underdark. You’ll have to kill the Master Brain (#12) to unlock this exit.