It was born to an old woman who had lived in the building previously and had a great attachment to her home.
The old woman was most likely a Watcher who had very little Life Energy so she remained unnoticed as if she had learned to pretend none of what she saw existed and that she did not pay attention to it.
There were plenty of people who denied what they saw and kept denying it while they found their way of living until the moment of their death.
The old woman who died created the Vengeful Spirit and was not introduced to anything related to the world she was experiencing so she did not know anything about what would have happened after she passed away.
Her obsessions stuck with her and formed her Vengeful Spirit which took the building as its territory.
She would not venture outside of her home and would continue to keep others out too.
