Chapter 562 - Advancing in the Dungeon
Like this, Sam begin to fight those Monsters while advancing. At that time you can say he already reach the peak Epic grade, and because of this all this time even though he was facing those abnormal monster, he wasn't having that much problem to fight them. It was just when to many of those Monsters try to attack team at once, he would feel quite hard to fight them because at the same time he need to careful from those dark spiritual energy that trying to effect him, and also most of them can uses the mind control attack and even though they unable to see his position, but after becoming alert everyone of them begin to use those technique to kill there enemy.
The thing was that in the first floor as you know he did not get any kind of reward even after killing those Monsters but in the second floor it was completely different and after killing those intermediate SSR grade monsters, you can say for the first time he receive a technique from that monster.