This guide will walk you through level 2 of Watcher’s Keep in the Throne of Bhaal expansion for Baldur’s Gate II. This area’s code in the game files is AR3016.
Watcher’s Keep Level 2 Map
Overview
When you arrive on this level of the keep, you’ll meet the Chromatic Demon (#1). He’ll be locked inside a cage, and he’ll make you a deal. He’ll tell you that only he can unlock the portal to Level 3 (Exit B), but that for him to help you out, you’ll have to free him from his cage. You’ll have to agree to this (now or later). When you do, the demon will tell you that four mages once worked on this level of the keep, and that for you to open the cage, you’ll have to collect their scepters.
To learn more about the mages, you should search their libraries (#2, #4, #7, #8) and talk to their unfortunate imp servant (#6). The imp will tell you that the mages’ labs (#3, #5, #8, #10) were powered by a “magical fan,” and that you’ll need to turn it on before you can find their scepters. Inside the libraries, you’ll learn ways to defeat the mages’ guardians.
Air Scepter
To start off, you should go to the Air Lab (#5). This is where you’ll find the magical fan. When you power it up (by turning the wheel in the center of the room), each character in your party will earn 20,000 xp. But at the same time, you’ll get attacked by two lesser air elementals, two greater air elementals, and a guardian of air. Lightning bolts will also start shooting out from some of the machinery in the room. This can make the lab a dangerous place to be, so for an easier time with the battle, you should camp your party in the hallway where you met the imp (#6), and then draw the enemies to you.
You’ll earn 40,000 xp for winning the battle, and you’ll find the Air Scepter on the guardian’s corpse. When you turn the wheel in the center of the lab while holding the scepter, you’ll switch the magical fan from “low” to “high,” and the machinery in the lab will stop shooting lightning bolts, making it safe again.
Slime Scepter
Next up, you’ll need to head over to the Slime Lab (#3). With the magical fan (#5) powered up, you’ll discover a poisonous fog in the lab, and you’ll have to fight a giant snake, respawning green slimes, and three poison mists. If you turn the magical fan to “high” and open the southern door from the Air Lab (#5) and the two doors to the Slime Lab, then the poisonous fog will blow into the Slime Library (#2), and the guardians will become more vulnerable (at least supposedly; we couldn’t tell the difference). The Air Scepter and the key from the Slime Library will allow you to open the three doors.
You’ll earn over 32,000 xp for winning the battle, and you’ll find the Slime Scepter on the corpse of the snake. You can also pick up the 
Flail Head (Poison) from the slime pool in the center of the lab. You’ll need it if you want Cespenar in the Pocket Plane to craft the 
Flail of Ages +5.
Note: By opening or closing doors, or by switching the magical fan between “high” and “low,” you can change where the poisonous fog is located. For now, it’s probably best to change the fan to “low” so the fog returns to the Slime Lab.
Ice Scepter
For the third scepter, you’ll need to head over to the Ice Lab (#10). The Slime Scepter will allow you to open the eastern door. Inside the lab, you’ll encounter three ice mists and an ice golem, but if you attack them, then you won’t be able to damage them. Plus, the coldness of the room will slow your characters down. Luckily, the creatures won’t chase you out of the lab, so you should be able to escape if you start an unwinnable fight.
To make the ice guardians vulnerable, you’ll need to open all of the doors between the Air Lab (#5) and the Slime Lab (#3), and between the Slime Lab and the Ice Lab, and then switch the magical fan to “high.” This will push the poisonous fog from the Slime Lab into the Ice Lab. When you enter the Ice Lab after doing that, each character in your party will earn 20,000 xp, and the ice guardians will become easily killable. You’ll just have to be careful. Since the ice guardians won’t chase you out of the lab, you’ll either have to kill them inside the lab with the poisonous fog hitting you, or try to zap them from the doorway.
You’ll earn 49,000 xp for winning the battle, and you’ll find the Air Scepter and a 
Horn when you loot the ice golem’s corpse. You’ll need the Horn if you want Cespenar in the Pocket Plane to craft the upgraded version of the 
Helm of the Rock.
Fire Scepter
And finally, you’ll need to head over to the Fire Lab (#8). The Ice Scepter will allow you to open the southern door. Inside the lab, you’ll encounter a fire giant and respawning greater fire elementals. As long as the fire elementals are around, the fire giant will quickly regenerate any lost health, and you won’t be able to kill him. Luckily, only the (killable) fire elementals will chase you out of the lab, and so you should be able to escape from an unwinnable fight.
To kill the fire giant, you’ll have to lure four fire elementals into the Ice Lab (#10). This will freeze them and permanently kill them. To make this easier, you should use the Ice Scepter to open the northern door into the Ice Lab, which will give you a straight path between the two labs. Each fire elemental you kill this way will earn you 22,000 xp.
With the fire elementals out of the way, when you return to the Fire Lab, the fire giant will no longer regenerate, and you should be able to kill him relatively quickly. You’ll earn 8000 xp when he dies, and you’ll find the Fire Scepter and the basic version of the 
Helm of the Rock on his corpse.
Chromatic Demon
When you have all four scepters in your possession, you’ll need to return to the Chromatic Demon and interact with his cage (#1). This will free the demon — who will then, of course, decide to attack you. The demon will switch between air, ice, fire, and slime forms, and he’ll resist most physical damage. So to kill him quickly, you’ll need to hit him with the elemental damage that his current form is vulnerable to:
- His air form is vulnerable to acid and poison.
- His ice form is vulnerable to fire.
- His fire form is vulnerable to ice.
- His slime form is vulnerable to electricity.
If your party is powerful enough, then you might be able to wear him down with physical attacks and not worry about his form. Otherwise, you should free him when he’s in the form you have the best attacks against — which is probably his ice form — and then blitz him when he exits the cage.
When the Chromatic Demon dies, you’ll earn 55,000 xp, and you’ll find the basic version of the 
Circlet of Netheril, 
Ixil’s Spike, and the Portal Key on his corpse. The circlet and the spike are both items that Cespenar in the Pocket Plane can upgrade. The key will allow you to use the portal to Level 3 (Exit B).
Walkthrough
1 – Chromatic Demon
2 – Slime Library
In the shelves in this room, you’ll find a Slime Library Note (a clue for the Ice Lab, #10) and a key. The key will unlock the western door to the Slime Lab (#3).
3 – Slime Lab
The doors to this room will start out locked. The key from the Slime Library (#2) will unlock the western door. The Air Scepter (see the Overview text above) will unlock the northern door.
Inside the room, you’ll find a large slime-filled pool containing the Flail Head (Poison), which you’ll need if you want Cespenar in the Pocket Plane to craft the Flail of Ages +5. However, every few seconds, a green slime will appear next to the door, and it will attack you. Green slimes are easy enemies, but they’ll hit you with recurring acid damage, which is annoying. So try to get in and out of the room as quickly as possible.
This room is also where you’ll find the Slime Scepter (see the Overview text above).
4 – Air Library
In the shelves in this room, you’ll find an Air Library Note (a clue for the Slime Lab, #3) and a Handwritten Note (a clue for Lum’s machine on Level 4).
5 – Air Lab
The southern door to this lab will start out locked. The Air Scepter (see the Overview text above) will allow you to open it.
This room is where you’ll find the Air Scepter (see the Overview text above).
6 – Imp
7 – Fire Library
In the containers in this room, you’ll find a Fire Library Note (a clue about defeating the Chromatic Demon, #1), a Handwritten Note (a clue for Lum’s Machine on Level 4), and a 
Wand of Cursing.
8 – Fire Lab
Both doors to this lab will start out locked. The Ice Scepter (see the Overview text above) will allow you to open the southern door. The Fire Scepter will allow you to open the eastern door.
This room is where you’ll find the Fire Scepter (see the Overview text above).
9 – Ice Library
Inside the containers in this room, you’ll find a Handwritten Note (a clue for Lum’s machine on Level 4), a Horn (needed for Cespenar in the Pocket Plane to craft the upgraded version of the Helm of the Rock), an Ice Library Note (a clue for the Fire Lab, #8), a 
Star Sapphire, and a 
Wand of Spell Striking.
10 – Ice Lab
Both doors to this lab will start out locked. The Slime Scepter (see the Overview text above) will allow you to open the eastern door. The Ice Scepter will allow you to open the northern door.
This room is where you’ll find the Ice Scepter (see the Overview text above).
Exits
- A) Portal to Outside.
- B) Portal to Level 3.
