Cost per tile: 50
Health per tile: 100
  Monster Attracts:     RoomSize:             Also Needs:

     Dragon                    25 tiles                         Lair
     Demon Spawn     25 Tiles                     Training

This is what being a dungeon keeper is all about:- the money! Your Treasure Room will not only be the place where you keep your bankroll, it will be the first room invading Heroes will seek out.
 Except for the gold that you start the level with, gold must be in your treasure  room in order for you to spend it. Generally, either you or your imps have to place the gold in a treasure room in order for it to "count". If an invading hero dies and drops gold in your treasure room, you still must pick it up and drop it to add  it to your total gold.
 The placement of your Treasure Room is extremely important. You want it to be accessible to your creatures on payday, as close as possible to the gold you are mining so your Imps don't have to carry it very far. One helpful technique is to build a Treasure Room right by the gold you are mining, then transfer the gold to your main Treasure Room by hand. It's a little extra work, but you'll accumulate riches much faster.
 Never have your Imps mine for gems while there's still gold to be had. Gems take a great deal longer to mine, so you should save them for when you need them.
When mining gems, build a Treasure Room as close as you possibly can to where your Imps are working, and cast Speed Creature on the miners (or make sure  they are level three or higher).
A final note on the Treasure Room: You can use your gold to make annoyed creatures a bit happier. Hit "T" to jump to the Treasure Room, grab a handful of gold, then hit "A" to jump to an annoyed minion. Drop the gold on him and he'll  be temporarily satisfied.
 
 
 
 

Lair:
       Cost per  tile: 100
       Health per tile: 200
 Monster Attracts:                    Size Needed:                     Also Needs:
Beetle                                          1tile                                   None
Bile Demon                                25 tiles                              Hatchery
 Dragon                                      15 tiles                            Treasure Room
 Spider                                        9 tiles                                Hatchery
 Tentacle                                     9 tiles                                 Temple
Vampire                                     9 tiles                              Graveyard

 The location and size of the lair is most important for keeping your minions happy.
 Make sure it's big, and that you have two or three if necessary. By building numerous lairs, where the majority of fighting among your minions will occur, you an keep Natural Enemies apart.
When placing lairs, it's a good indea to consider the path that invaders must take to reach your Dungeon Heart, and make sure that they have to pass thru at least one large lair.  That way, any resting creatures can act as guards while they rest.
You can assign a creature to a given lair by dropping him into the lair where you  want him to sleep. This is especially helpful with Horned Reapers and Vampires, both of which can get a little testy when near others. Your lair should also be big, probably bigger than seems necessary. Breathing room keeps your creatures happy, and an overcrowded lair can lead to some rampant dissatisfaction. As a rule, your minions require only one tile for a sleeping area. The exceptions are Dragons (two tiles), Bile Demons (four tiles), and Giants (two tiles). Imps don't  sleep, and therefore don't need any lair space.