D-Rank To B-Rank

In silence, Albrecht led the Grapevine Party to the corner of the Fifth Outerlayer where the Hidden Dungeon was located.

As accurate as its name, the Hidden Dungeon couldn't be seen by naked eyes, nor could it be detected by any aura detection skills.

The only way to access the Hidden Dungeon was through the Black and White Key that Albrecht possessed. Once the Black and White Key was in the vicinity, the Hidden Dungeon would open up.

Even then, one wouldn't be able to see nor detect the Hidden Dungeon. Based on the information provided by the System, the Hidden Dungeon was only discovered after a couple of years. A certain adventurer randomly walked into the Hidden Dungeon after he got the Black and White Key. He had no idea where the key would fit, so he combed the entire first five outerlayers.