The Library is an essential part of your dungeon. Without it you won't be able to build advanced rooms or cast spells. You should make your Library as efficient as possible - make it square, build it away from the more active rooms, and reinforce the walls.
Under no circumstances should you build a doorway leading to a Treasure Room or a hatchery from your Library. While your researchers may have to walk a bit to eat or get paid, other creatures won't use it as a hallway - a quick way to annoy your Warlocks, who will eventually open fire on trespassers.
Warlocks and Dragons will spend most of their time here, but you should take them out for the occasional training session. Warlocks are great ranged fighters at higher levels but terribly weak at lower levels.
Once your research is complete, don't sell off the Library no matter how tempting it may be. If you sell sections, you'll lose the spells stored there.
Here is the order of research in the Library. The first ten will already exist when you start your dungeon:
| | Research | Type |
|  |
| 1 |
Magic Hand* |
Magic |
| 2 |
Possess Creature* |
Magic |
| 3 |
Slap* |
Magic |
| 4 |
Create Imp* |
Magic |
| 5 |
Dungeon Heart* |
Room |
| 6 |
Treasure Room* |
Room |
| 7 |
Lair* |
Room |
| 8 |
Hatchery* |
Room |
| 9 |
Training Room* |
Room |
| 10 |
Library* |
Room |
| 11 |
Sight of Evil |
Magic |
| 12 |
Bridge |
Room |
| 13 |
Speed |
Magic |
| 14 |
Must Obey |
Magic |
| 15 |
Guard Post |
Room |
| 16 |
Call to Arms |
Magic |
| 17 |
Workshop |
Room |
| 18 |
Conceal Monster |
Magic |
| 19 |
Barracks |
Room |
| 20 |
Hold Audience |
Magic |
| 21 |
Prison |
Room |
| 22 |
Cave In |
Magic |
| 23 |
Torture Chamber |
Room |
| 24 |
Heal |
Magic |
| 25 |
Temple |
Room |
| 26 |
Lightning |
Magic |
| 27 |
Graveyard |
Room |
| 28 |
Protect |
Magic |
| 29 |
Scavenger Room |
Room |
| 30 |
Turn to Chicken |
Magic |
| 31 |
Disease |
Magic |
| 32 |
Armageddon |
Magic |
| 33 |
Destroy Walls |
Magic |