In the Shadows house wiki they mention,
Unification : The process the newly invited shadow will go through after being invited to the Adult's Wing. The shadow-face pair are put together inside a Box of Completion, with the shadow forming a cocoon from one to three weeks, where they will either unify or die. Unified shadows gain control of their living dolls' body whose consciousness will no longer exist. After this, the newly emerged shadow is considered an adult.
Due to the tragic end of the living doll in case of success, and the death of both if it fails, this process is kept an absolute secret from the children. As measures against leaks, adults can only appear in the Children's Building in special occasions and they are not allowed to show their faces. Children are to not mention the name of invited pairs for the same reason.
What do shadows and dolls unify for? Do they get some additional power, intelligence, lifespan, emotions or something?
