What is Luck and what does it affect?Luck is a completely random component of every fight. Your Luck will be somewhere between -25% and +25% and it is always given from the attackers point of view. If you are attacking with +25% luck it means that your fighting power is increased by 25%.
There are also Luck flags. Luck flags allow their owners to predict the outcome of their attacks by manipulating the "Luck" factor in battles. These mysterious flags will force luck as near to 0 as the strength of the flag allows. If a battle would have -20% or + 20% luck, a 6% flag would force the luck to -14% and 14% respectively.