The Dungeon of Unique Magical Power [1]

After three days, when Mayquelle, Ian, and Baron had finally prepared their equipment and themselves for the mission, they went straight to the entrance of the dungeon they were assigned to investigate.

Every dungeon has a vortex-like entrance that seems to be a portal commonly called "rifts." In these rifts, it is explained that no normal person can enter them without proper equipment. 

First, because the density of mana could rupture the skin of a normal person, only those who can enter are Awakens with the proper suit as security and for their safety.

Second, they needed to wear a proper suit to provide a track of their progress inside the dungeon. A dungeon is another dimension that has space. Thus, with suits that possess special mechanisms, they can produce a map of it and save this information for future expeditions.