To elaborate a bit further: let's say there's a planet in which some higher power installed several giant "domes" where people live. Each of these domes, which are the size of a small city, contains a totally different primitive civilization, with different traditions and even languages. Each dome city is unaware of the others, and also unaware of the fact that they're inside a dome (they're kept inside via some high tech stuff that makes it a real life loop, so that's the entire land for them).
The 'higher power' occasionally sends people to these villages, where they present themselves as a different thing depending on the dome, and while down there they use all kinds of advanced technology to trick the villagers into thinking that they have (or are) supernatural entities (for example, in some domes they present themselves as your average fantasy saga wizards, while in other dome they are seen by the villagers as ghosts).
In order to keep developing this world I have to come up with a reason for this weird setup. The outside of the domes is habitable but barren, and the 'higher power' people usually come down from space to carry out missions inside a dome.
I have one possible explanation for this setup and the meaning of the missions, but I have some issues with it, that's why I wanted to get some more alternatives before choosing a final one.
The higher power is actually a group of sociologists that try to replicate different types of civilizations and they send enforcers to apply some type of input to the civilization, measure the output and try to model them / predict behaviors.
A problem I see with this idea, besides it being too close to far fetched for my taste, is that at some point the domes would be 'unusable' from a sociological perspective, as the 'enforcers' can push the people in it too far and destroy their delicate balance as a civilization. Why would an advanced civilization go through that effort to ultimately have the civ destroyed if one of their hypothesis happens to fail in a big way?
Answers can be either new and totally different from mine, or to elaborate/give more support to my justification.
EDIT: Thanks to all of you for your answers! Each one helped in a different way. I choose as answer the one that made me think the most about my justification and expand it in a believable way.