The Dark Knight System is a series of four different challenges that focuses on various aspects of the game. Each set is made up of 15 individual ranks that must be done in order. For example, you must do the first rank for Shadow Vigilante in order for the second one to appear. You will get rewarded with upgrades for gadgets, as well as experience.
Note that sometimes certain gadgets or upgrades may be required to finish some of the objectives. Also, some of the objectives may only be finished at certain sections of the game, so it might be helpful to read through them before progressing into the campaign too far.
