Great March missions are usually active at the same time as a different event and send you into battles against huge numbers of monsters. These take place on one map, but with different numbers of enemies depending on the difficulty chosen. These missions have no stars, and provide no Experience, Gold, or Unit drops. Even if the player runs out of lives, the number of monsters killed will simply be tallied, and it will not technically be a failure.
There are 2 different reward scales, one for most killed monsters in one try and another for total number of monsters killed during the event. The missions cost Charisma to play.