In Japanese mythology, a kekkai (血塊, lit. blood lump), is a blood homunculus created during a childbirth that is not sanctified.
Appearance
The kekkai is a hideous, amorphous blob of blood that lurks about and frightens people with its horrible appearance.
Origin
Due to all the taboo surrounding blood in Japanese culture, a special ceremony must be performed to remove the impurity. If this act was not performed, a kekkai was formed and created havoc and fright among the village until the rite was completed.