"If the marks are more permanent, we need to search the ground or buildings." The scattered nature of setup means anchoring anything to a stand would be unpredictable. It makes more sense if someone (or someones) came through and carved things into the ground or buildings before the festival went into full swing.

"On the other hand, when the cult created that blighted area, they formed a large circle and chanted something. I didn't see any runes on the footage I could find. Maybe we should look for security cameras anyway."