quote:

Somewhere option at the Crossroads, there is a (star lvl*3)+6 = % chance of encountering a Rare Treasure Chest at the end of each chain of battles, provided you are at least L30.

"Star lvl" : Crossroads is divided in to 6 distinct location based on battle background. Each of these locations has a sign post associated with it. Upon completion of the location either directly or randomly from Somewhere the corresponding location with go up one "star lvl" to a max of nine.