Nix's capture of the boss caused a snowball effect.
Alex and her could command the army of spiders at their will and due to this, they ended up finding many hidden spots at their floor and also got to know of the identities of the people fighting here.
The people were ordinary Blesseds and had little to no connection with anybody other than being given quests by their Gods.
The hidden spots ended up being more useful than them as there was a hidden pathway that led directly to the last floor of the dungeon, saving Alex and Nix a lot of trouble.
Alex wasn't getting any benefits anymore by consuming monster cores and it was better if he just left the place with his wife.
They reached the outside of the boss room and hid until the rest of the people came to fight.
Once the boss fight began, Alex and Nix hid themselves again and eventually, in a really anticlimactic manner, the fight ended and they were out of the dungeon.