The Soul Jar is a large, glass cylinder in Arrival.
When any being dies, its soul can be seen to leave its body as a grey, ghostly form. Viewing this is generally con-sidered to be unpleasant, as souls clearly do not enjoy the process. They can then be seen to move, seemingly against their will, toward the middle of the world. Residents of Arrival routinely see these souls move toward the center of the city, under the enormous city-covering tarp, where a giant glass jar sits. Souls are sucked through the holes in the metal lid of the jar, and drift around inside. It is said that individual souls could be seen in the jar when the world was new. Now only a grey cloud is visible. Most people consider this to be evidence of an unpleasant afterlife, though others argue that only everyone’s evil nature goes in the jar, with the better parts of their being going somewhere else.
There are stories of souls who have had their journey interrupted and ended up in a different body, or wander as ghosts, or entered the jar but were somehow drawn out. There are probably academics who research such topics.
it's a jar of souls lol