Dungeon Keeper

In Dungeon Keeper you own some prime subterranean estate that is ripe for dungeon development. Starting out with a few bare rooms and corridors populated by a smattering of imps you must expand your underground empire wiping out all before you. You direct the movement of all your minions from a rather nifty isometric viewpoint where you can rotate the map by pressing the 'control' key with the cursor/mouse. Once you've got used to the controls, which shouldn't take long, it's time to fit out a room to accommodate your treasure and then start digging out your new empire. You won't get very far unless you find some gold, so dig south and you'll eventually come across a great seam of the stuff. Soon enough you'll run into other dungeon like you, are out to expand their underground borders and they too will have troops to do their bidding. This is where the fighting starts, and rather than just stand by and watch the carnage, you can dive in and see your world from their point of view by casting a 'possession' spell and moving the critters about using the cursor keys and the mouse. When you've had enough of life as a mere mortal, go back and direct the action from on high. When you've had enough of the demo, well you'll just have to go out and buy the full version, won't you!