Responses
Basically, in addition to the kids' trauma, he looked at the description of one of the boss monster's skill card, which is to create a field of fire where no one can leave without the boss's permission. He also remembered that the Black Witch's guild was able to safely leave when they did not beat the boss.
This is because the boss monster just wanted to someone to play with before they move on. That is why Gongja plays hide and go seek with them and tag all the dolls until he reaches the main doll so that they can leave in peace and joy.
i'm confused as to how he cleared the tenth gate? yes he found out about the trauma and gave them closure, but how did he come to that conclusion? is it lost in translation?