82nd floor
The group took four days before they found the entrance to the 82nd floor. The monsters on the 81st floor were few, but the maze was confusing them, so it took days before they found the entrance to the next floor.
A labyrinth like this could be cleared by a power of S-rank or above. That's why most of the living labyrinths in the Imperium were gone, because every time they discovered one, a lot of powerful people tried to conquer it and acquire the god's legacy. Sometimes gods appear and take it for themselves.
The only known living labyrinth that couldn't be cleared was the Great Labyrinth near the True God's Holy Kingdom. Even gods couldn't clear that terrifying labyrinth that could even swallow immortals.