The Seam is a place, like a purgatory, of passage where the human soul passes to reach the afterlife.
Overview[]
For the Egyptians, humans are composed of two elements: the Ha, body, and the Ka, soul. The Egyptians also believed death is not an instantaneous change of state, but a process where the soul moves from one realm to another: when death occurs, the soul vacates the body and passes into the Seam, from there it transitions to the Beach, and only then on to the world of the dead. Some people, known as repatriates, have the power to guide their souls, after being "eaten" by a BT, in the Seam by following "strand", ultimately bringing themselves back to life if they find their body.
It has the appearance of a seabed where various forms of marine life (whales, fish, etc.) swim upside down. Whether these creatures are real or a form of projection is unknown. Other life forms are cryptobiotes, organisms that seem to travel across worlds as specimens are found in the living world and on the Beach, and coral-like. The coral-like organism, like the real coral, is older than any organism of the land, and hardy enough to have weathered the mass extinction of 540 million years ago and for this have probably develop an ability to live between life and death, between time and timelessness, and like the cryptobiotes, survive into the Seam and in the world of the living. It is also a lifeform upon which many other organisms rely for survival, like the cryptobiote who nest inside it.
White version of Catchers, a large form of BTs, appear to swim both in the Seam and on the surface, where they "eat" the souls of the resurfacing dead.
Notes[]
Since the Seam is a gateway world for souls, and due to the presence of BT Catchers, probably the "water" of the Seam is part of the tar that seeps into the world of the living and used as a medium for the gateway.