All creatures, buildings, and traps:
At the Main Menu, type please give all.

Moon Levels:
Some levels only show up during a full moon. The program determines this by your CPU clock, which can be changed. If you play the game with the date set to a full moon, you'll see one of these levels denoted by a flag witrh a circle. So get out the almanac and start exploring!

Skirmish Mode:
Solved the game? Can't find a biological opponent? You can play all those multiplayer maps against the computer! Just go to your DOS prompt and start the game using '-1player' as a parameter. In the following example you should be in your Dungeon Keeper directory:

C\>keeper95 -1player or C\>keeper -1player

Thief to Lord. Demon to Dragon:
If you have a level 10 Thief or level 10 Demon Spawn, keep training them. The Thief will turn into a Lord of the Land and the Demon Spawn will become a level 4 Dragon.

Sacrificing:
One of the biggest mysteries in Dungeon Keeper is what to sacrifice at the temple. Temples also make your monsters happier, can cure them of disease or chicken-ness. But the most fun is to drop your creatures into the temple waters to see what happens.

Here is what we've found so far:

Imps - Sacrifice a few of these little guys and they get much cheaper to create! Well worth it.
Fly & Spider - Get a Warlock
2 Beetles - Complete current manufacturing
2 Flies - Complete current research
Beetle & Spider - Get a Dark Mistress
3 Spiders - Get a Bile Demon
Ghost - All your chickens die
Vampire - All monsters diseased
2 Bile Demons - All monsters turn into chickens
Horned Reaper - All monsters angry!
Dark Mistress & Bile Demon & Troll - Get the Horned Reaper or sacrifice a Bile Demon , Dark Mistress , and a Imp

Do NOT sacrifice the undead or chickens, unless you like making the gods angry.

Speaking of the Horned Reaper, he's a great fighter, but can go a bit bezerk at times. If he gives you too much trouble, you can pay him off by dropping money on him. Makes him happier (me too).

Thanks to Revolution readers Adam Darwish, Molta Belly, Fred_ij7, Colin Farquhar, Cecel, Sangokuuty, and Martin Brodeury!