The Hollow
What is left when an un-selfing fails: a husk that keeps reaching, scraping fragments of other minds together just to have something where a self used to be.
What a Hollow is
A full hollowing empties a person completely, and what remains goes still or feral. A Hollow is the rare botched case, where the emptied husk doesn’t stop. It keeps reaching into nearby minds and taking pieces of them, to fill the place where a self used to be.
Its victims end one of two ways: catatonic, emptied out, or hunting, aware of the absence and driven to take from others in turn.
A witch, and a Hollow
A witch and a Hollow work in the same space between minds, but they commit different crimes. A witch takes memories and leaves the self standing, intact and a little less. A Hollow takes the self. It leaves nothing that was you at all.
A witch is a burglar who leaves the house standing. A Hollow takes the load-bearing walls.
No foothold
A Hollow has no place of its own in the physical world, and it cannot use the Tide. To cross, it has to manufacture a way through. Lethe, the first Hollow anyone knows of, needs ten gathered minds to do it.
Who performs the original hollowing is not known. It may be one of the Old Monsters. It may be something older.