FAQ 5.1 - Where can I go to kill things?
You can attack nearly anything, but the odds are good that you'll pay for it if you attack things in the camp or in major cities. It's always a good idea to use the 'consider' command on things before attacking. When you start out in the various new player areas, you will be directed toward areas that are safe for you to fight in. In the newbie quests, there are a lot of monsters in the fields and graveyard.