Yes, we get more rooms. Build your standard rooms. If possible, always build your training room "towards the enemy". That way, when they come at you they have to go through your biggest concentration of your strongest monsters.

You get a library. Build it somewhere QUIET. And somewhere by itself. Warlocks work best when it's quiet there, and hate people wandering through their library! Put it way off to the side somewhere. As soon as you have "researched everything", train your warlocks in the training room. They train very well. Train everyone until the Lord decides to come a-knocking.

Note that there's a secret room you can dig to to the SW.

Dungeon Keeper Walkthough Index