“Demons” is episode eight of season three of Stargate SG-1.
SG-1 arrive on a world with what appears to be a medieval Catholic population, apparently of English descent. This is the first time Christianity has been encountered, and this is also one of the more modern cultures discovered. By quite a long way. In fact, the only probably comparable ones are the Norse-based associated with the Asgard.
The team are mistaken for demons, as they came through the stargate. In this case, the Goa’uld isn’t playing god, but Satan himself, and he requires sacrifices to him.
The demon is the same species as Unas, the first Goa’uld host (the Unas seem to be a race now, not an individual), who was encountered in “Thor’s Hammer”, and seems to be working for Sokar.
The culture fears demons, but does not worship them, so being mistaken for demons causes problems.
I’m sure Unas’s race reminds me of a race I’ve seen in something else. Maybe Star Trek?