Chapter 609 - Hion symbol
Sam already contacted the president and he already began to explain all the details that he found until now. He also began to tell him the current details that both of the elders told him while examining the bodies of those dark humans.
First of all, that weird symbol present in the forehead of those dark humans, not only works as a container for that berserker spiritual energy, but at the same time, it also works as a container of dark spiritual energy.
Also because of that symbol, all of those dark humans had that strong barrier in their mind and it also has the mechanism that if someone tries to break that mental barrier those dark humans will immediately die. Not only that it will also send a signal to the mastermind who put those symbols on the forehead of those people.