Chapter 561 - Abnormal State
At first you can say that he wasn't having that much problem to kill those Monsters even though Monsters were much powerful compared to your normal Monster present in the danger zone. But using the origin spiritual energy he could easily kill them and because of this he easily clear the first floor and already get ready to go to the next floor.
But before that he naturally needed to recover his spiritual energy and health. Even though killing those Monsters was easy but the thing was that the number of those Monsters much bigger and because of this he also get injured while fighting then and already lost some of his health points.
The thing was that he really did not know why everyone of those Monsters were that much powerful compared to you normal Monster and also everyone of them releasing that abnormal dark spiritual energy. Moves likely if it wasn't for the origin spiritual energy than until now he would have been affected by the dark spiritual energy.