|Gender||Unknown (portrayed as female)|
|Appearances||Forbidden Siren 2|
|Voice Actor||Mai Takahashi|
Long ago, the Ancestors fled to the World of Nothingness to survive after being chased by the light, losing their forms after a time close to eternity had passed, finally merging into one consciousness. 44 years ago, due to the effects of Yamijima's development, a "phantom" of the real world Yamijima appeared in the World of Nothingness, and Mother began to stir from her long sleep. 33 years ago, a small rift created between the real world and World of Nothingness allowed a drowned body to wash through; her image was copied by Mother, allowing her to give herself a form. And then, 29 years ago, Mother birthed an Offshoot of herself possessing a temporary body to search for a means to evade the effects of the light, wishing to return to the Earth's surface, sending it to assess the situation in the real world. After releasing several doves, Mother confirmed that she could return to the surface using a human shell, and began efforts to reclaim it.
Since Mother is made up of the Yamirei, an intelligent body made of pure energy, she is able to use many supernatural abilities such as creating things from nothing and dragging people to the Reflected World from the real one. As viewed by humanity, these could be seen as the actions of an egotistical god.