Imperian has hundreds of help files to help you learn more about the game and how to play.
4.10 The Defences Command
Typing DEFENCES or DEF will show you a list of what beneficial things are affecting you. Generally there will be one line listed for each defence or effect. DEFENCE DRAINS will list the defences you currently have that drain mana, and how much they are draining. DEFENCE RAW will show you a list of your defences, using their raw name rather than defence message.