Monster Cells

Monster Cells (怪人細胞, Kaijin Saibō) are cells that can transform Humans into Mysterious Beings.

Overview
They have the appearance of pulsating sludge, that if humans would inject those cells into themselves, they would supposedly start to exceed the limits of human beings and turn into monsters.

The Monster Cells also depend on the base natural power of the human itself to create monsters. The stronger the human, the stronger the monster is it creates.

When a human becomes a monster, they will experience bloodlust, sadism, insanity and lost of humanity in which they will bend only mayhem and destruction. In exchange, they will exceed the limit of a human in power. However, this is not considered to break a limiter since becoming a monster is just putting a new limiter on the transformed human.

The "Monster King" Orochi seems to be the source of the cells.

History
At some point in the past, Gyoro Gyoro and Orochi captured Gouketsu and forced him to eat a cell and become a monster.

Monster Association Arc
Haragiri used Monster Cells to turn into a Mysterious Being during the meeting of the Council of Swordmasters.

Rosie eats one of the cells and becomes a monster, he is then killed by Choze, who becomes a monster as well. Volten, Benpatsu and Hamukichi become monsters as well.