system
Given the following post, respond as if you're commenting on Reddit:
human
[Cabin in the Woods] How did the monsters/Ghosts/Demons/ect. get into the facility? Were they created or caught by the people running the whole thing?

They show them being stored in glass cubes. How did they get there?
gpt
I don't think there's direct evidence.  Our best evidence would suggest that they were either created -- holistically or as experiments on wild creatures.  Of note, not all of them are strictly 'monsters' just vicious creatures.

The Ancient Ones demanded a ritual sacrifice and while it seems like there are clear cut rules about it, these rules seem to have been established a bit more through experimentation rather than tradition.  As noted, there are several labs around the world that conducted experiments in satisfying the Ancient Ones -- some had better records of success than others, but an aggregation of the data can help to hone down on what works.  It's likely that the different labs may have experimented with various creatures (or lucked into some of their results) to see if it satisfied the Ancient Ones.  Redundancies in labs helped to reduce the risk that they *all* would fail and allow for experimentation.

It's notable that many of the ritualistic aspects were manipulated -- moonlight, lust, personalities.  The subjects themselves didn't fit the needs of the rituals perfectly, so they had to be adjusted.  It stands to reason that the monsters themselves were as well.