- Catching and containing ghosts is a big part of the story, which often isn't something portrayed as possible in other ghost centric franchises, and the tech for trapping the ghosts could have been ripped off/reversed engineered from ghostbuster technology.
The Great Child, Dire Mother, Jackal and Juggernaut are related to each other, most likely as cousins.
- That would explain why they all had physical or mental abnormalities, or were more predisposed.
- Granted that they together spanned about a century of time, with the Dire Mother being around the later 1800s to early 1900s, and the Jackal at the same time. The Great Child was around the early 1900s to maybe around WWII (guessing on the story) and the Juggernaut around the later 1900s (maybe 1970s or 1960s, to early or mid 1990s). Can't say how closely related they would be though.