Osta was also a Mobile City, except it was an "unfinished" one.
According to the blue-haired boy, before the Great Cataclysm arrived, the people here had indeed tried to build a brand-new Mobile City centered around this hill. But then a problem arose: Wula's mother became pregnant and gave birth.
However, Wula's mother had not wanted to have a child. Her health had been poor at the time, and she apparently did not love her husband either. Yet no one cared about her wishes. The whole world had already begun to "twist," and fewer and fewer children could be born, so she had been more or less forced to give birth.
That was why, when the child was born, people had swarmed in to save the baby and abandoned the mother—in their eyes, it had been a perfectly reasonable choice. After all, children were almost never born in this world anymore, while the mother was frail and sickly, on the verge of death, and could never have another child.
Save the mother or save the child? To the people of that time, that had not been a question at all.
Naturally, Wula's mother hated all of it. Looking at those people who held her child in their arms while utterly ignoring her, she spat out a curse of rage, grief, and hatred—and made a wish.
She begged for people to die.
And her wish was accepted by the child who had just been born—or rather, by one of the children.
That child was Wula.
She accepted her mother's wish and became the symbol of death. Those she gazed upon would die. Those who heard her wail would die. Those who touched her would die as well—then rise again, continuing to exist in this world in the form of the dead.