Chapter 139: Darkened State

[Barrier Turtle (Darkened State)

A State brought upon by consuming the Mad Stone that was made from the bones of 100 mad Beasts and by sacrificing a 100 people together with the Beasts. 

A stone that if consumed, will make its user become stronger for a short period of time in exchange for their sanity. 

It has been banned since ancient times as it torments the mind of the user and the Summon.

Mad Stone can be consumed by the Summoner and the same effect will occur to the Summoned Monsters.

...

]

The knowledge regarding the Mad Stone and the Darkened State that Tori was in was immediately injected inside Ban's head. He was able to comprehend it almost instantly and he now fully understood how it works. 

In short, it was an evil stone that can be produced by killing 100 people. In order to make it, one would need to refine the 100 people alongside the bones

  of 100 mad Beasts.