The residents of North City were the ghosts formed after the death of cultivators. Not all died due to the exhaustion of their lifespan, some were killed by others, leaving only their incomplete souls that fled to the Netherworld to barely survive.
In any case, although the origins of these ghosts were exceedingly complex, they all shared one common trait—they were extremely powerful.
After their deaths, they did not wish to undergo reincarnation but chose to forcefully linger in the Netherworld, attempting to resurrect and walk the path of Immortal Dao again.
As for why they were unwilling to reincarnate, the reason was rather simple. If their cultivation hadn't reached the level of a Golden Immortal, without the protection of the immortal Dao light, then entering reincarnation would subject them to the influences of the mysteries within the womb.
