It didn't take much time to complete the dungeon run as Chris thought.
[Congratulations player "Voyd" for clearing the Attribute dungeon in Nightmare Mode.]
[As the first to clear this dungeon, you would gain ownership of this dungeon.]
[You have gained an Attribute Dungeon Core.]
This was the same notification that he got when he completed the attribute dungeon back then.
After the dungeon was conquered he was ejected from the dungeon.
He reached out to the core in his space, "Create a dungeon in nightmare mode".
[Command received.]
[Nightmare Dungeon in creation...]
[Time left: 02:30:00]
"System, take me to the safe zone".
[Player being transported to the safe zone.]
Swoosh!
Once inside the safe zone, he checked the time.