It’s a fictional town loosely based on Centralia PA:
" Silent Hill 's screenwriter, Roger Avary, used the town of Centralia, Pennsylvania as an inspiration for the town of Silent Hill ;" - Wikipedia
The town of Silent Hill has enough backstory to see that’s it’s a mishmash of many stories, I think. The plague and the wars happened as told, but so much happens to that one place it’s easier to imagine that was multiple events being superimposed. And of course all the geography and names are invented.
(E.g. it’s on a “Toluca Lake” in Maine, which doesn’t exist. The only Toluca lake in the US is in Los Angeles, California).
I guess the circle looks like a summoning circle more than a sigil?
The cult wasn’t evoking though I don’t think… seems they would have put the girl in the circle and called the entity into her as a possession. I think you could use that to evoke into.
But we already know Samael and can work with him anytime.
But if it’s a sigil, could it be used with to evoke the games thoughtform version of “Samael” to talk to it, formed by the game makers and your own expectations, what would you get?
It would be interesting to scry into it and find out.