Their mission was simple and straight forward. But the danger associated with it was also great.
They needed to reach the deepest part of a treasure vault, defeat the boss monster there and then bring a special item called "Mirror of Calling" back.
This treasure vault was created by a powerful magus and this mirror was something that he had stolen from a friend of his. So the family of this friend had given the mission to get the treasure back.
As for the monster that was present as the boss of this place, it was an Undead Dragon created because of the experiments that this magus did. Even though defeating it was the mission, Shin and all his party members were actually planning to capture and tame this undead beast for Ellie.
Obviously capturing such a powerful beast was definitely harder than just simply killing it. So for their future growth, the Shin and his team were taking a huge amount of risk.
