Right now Sam is facing many epic grade monsters. But none of those monsters are attacking him all this time because they can feel the power of Sam. This is the reason that all the Monsters maintain the distance between him and them.
It is just Sam did not make any kind of move right now and because of this all those Monsters even though they get the chance to retreat from that place they did not decide to retreat and stay there. As you know the intelligence of those Monsters wasn't that much and because of this, nobody can guess why the hell those Monsters did not retreat while they got the chance.
Instantly all the Monsters feel a huge pressure that affect their whole body. That pressure directly came to their body while you cannot sense any kind of spiritual fluctuation or spiritual pressure on that place. That also make all the Monsters very confused as only some of those Monsters get affected by the pressure suddenly.