Not much is known about these mushi except that they once existed on this earth and sought to kill all other Life including other mushi, flora and fauna. At one point a Mushi master sealed them inside the Karibusa family.
No record of the Mushi's appearance has been recorded and nor how it was sealed into the Karibusa family. All thats known is that Tama's ancestor sealed away the mushi into Karibusa family. The person whom the mushi was sealed into was pregnant at that time. The side effect of the seal was that she developed coal like marks on her body. Ever since then once every few generation a child with the coal like birth mark is born and the part of the body with the mark is rendered useless.
The person with the birthmark is called a Scribe and they can completely cure themselves by writing down stories of how other mushi have been killed. The process itself is very painful to the scribe, by writing down the person seals the forbidden mushi away in these scrolls. The scrolls are stored away in the Archives. But as the scrolls grow old the text in them needs to be copied into new ones. Till date no one in the Karibusa family has managed to completely seal all the forbidden mushi away inside them.