To those who cleared E-7 and other maps in harder difficulties, good luck on finding those 3 event ships. It's not easy farming ships due to RNG trolling you so hard, taihaing one or more of your ships as you go to the boss node. And when you did get to the boss node and defeat it, a large chance that you get loots that you don't want.
To those who alreacy cleared the event, Congrats for clearing Summer Event 2015 and Good Luck to those who will farm for those event ships.
