Expert Difficulty Enemies Only As Powerful As Beginner:

Begin a battle under the expert difficulty setting. Save the game and quit immediately. Then, change the difficulty setting to the beginner setting and play any Legend. Defeat five or more troops then press Start + Select to reset and continue the old Legend. It will count as expert mode, but the troops and generals will have 20% less defense and will be easier to defeat. This trick is very useful for unlocking level 11 weapons, especially for Lu Bu.