Outsider's Gate is the fifth stage in Stories of Legend sub-chapter 20, Silk Road.
During the Battle
The Enemy's Castle will spawn more enemies: 1 Squire Rel, 1 Master A. or 3 Owlbrows
Strategy1: You will need heavy attackers, such as Bahamut, Ururun, and any uber rares to deal with the owlbrows, it is highly recommended you use Jamiera Cat and Crazed Mythical Titan Cat to hurt the master A's. However, the master A's spawn continuously, so the Titans will be unable to hurt the master A's meaning long range attackers, like hacker cat, are mandatory. Strategy2: It can easyly be beaten, by waiting for the owlbrows, to get past the master A, killing them with something like king dragon and crazed dragon and crazed wall. Then just spam titans, dragons, crazed whale, hacker cat, crazed gross and everything, that can damage the master A's. The Owlbrows should keep your money up.