These three places, aside from the Eden Hotel where real Cursed Spirits are suspected to exist, the previous two are undoubtedly stemming from Quasi-curse spirits!
And... they all have a multitude of duplicates!
The duplicates of Quasi-curse spirits... must harbor some secret or mystery, yet, to this day nothing has been unraveled within the hospital.
Director Lu Ping had posited a hypothesis in his paper he wrote: the reason Quasi-curse spirits need duplicates is due to some kind of limitation.
The very essence of a Cursed Spirit is symbolic of Rules, and while this curse is indeed powerful, it also means that Cursed Spirits cannot kill at will—they must follow certain patterns. For the same reason, for a Quasi-curse spirit to transform into a Cursed Spirit, shedding the "quasi," it must also adhere to certain Rules.