Agares put the books back on their shelves. He had learned enough about what happened on the 80th floor and the truth about that adventurer.
In short, he couldn't move up to the next floor not because he died on the 80th, but because the dungeon blocked him.
He couldn't go on to the 81st floor because he didn't have the Saber sigil on his hand.
Agares turned and saw Aoi still jumping happily on the bed. He called Aoi to return because they had to keep exploring the dungeon. Aoi obeyed and walked toward Agares.
"Did you find something from the book?" asked Aoi, curious.
"Yes, maybe some kind of clue."
"A clue to defeat the monster?"
"Haha, something like that."
They walked back down the dungeon hallway, leaving the room open with its broken door.
Looking at the smart navigation Agares activated, the actual boss room was in the hallway in the middle.
