This isn't a ritual so much as a custom, but I think it still kind of fits the question so here goes...

I haven't reached the culture-building stage of Erziyye yet but this is one of the ideas I know I want to include somewhere. However, I haven't picked the culture yet so some of the details are a bit vague.

Basically this culture believes that children are born without souls, and that it is the love and connection with the mother that attracts a soul to the child and causes it to become ensouled, as it were. A person who reaches adulthood without this happening is considered very dangerous because they are believed to be violent, unpredictable and without conscience. This makes children whose mothers died in childbirth a problem socially. In the old days, they used to just be left in the woods, or raised by a foster mother (who was considered as good as a real mother), depending on the region. Eventually as the society became a bit more inter-connected, and the beliefs became a bit more formalized and just changed with this, there grew a belief that just any old foster-mother wasn't good enough. A system of special orphanages was developed where these children were raised. In these orphanages, there would also be a number of teenage girls staying who had themselves been orphans at the home once upon a time. These girls were encouraged to spend time with the children in the hopes that they would form a bond that might ensoul a child (being themselves children of mothers who died in childbirth, they were considered to have a sort of blood connection to the other orphans that regular foster mothers wouldn't have). If an ensouling happened, the girl could then leave the orphanage and take the child with her, or send the child to live with her family and stay behind in hopes of claiming another child (the former being more common). Children who had not been ensouled by the age of 10 (or so, haven't decided exactly) were considered to be lost causes and killed in a yearly ceremony. I haven't decided the details of the ceremony yet, so I don't know if it's literaly bloody, but I find the idea, of these teen girls being caught between knowing these kids will die if they're not claimed and being constantly told how special and holy their role as foster-mothers are, how they'll know "instinctively, beyond any doubt" the moment a child is ensouled and how dangerous it would be to bring home a soulless child, to be pretty grim.

I'm not sure how well I've explained it here but oh well.