You hide away and observe the camp for a couple of hours. The celebration inside seems only to get rowdier. It's hard to see the layout of the camp from where you are, you'd probably need to climb onto the plateau and walk further in to see everything, but as you look closer you can see several circular huts made out wooden stakes, hide, mud and sod. They're crudely built and decorated with skulls and you mainly see kobolds around which seems to indicate that this would be where they're staying. You can't see any tents from here that would indicate where the cult's leadership would be.
More importantly, you see from a few stragglers arriving after you, you notice that they just walk in. No one seem to accost them, the security seems barely existent. No one are wearing cultist outfits. There is reason to believe that you might be able to blend in, unless you were unlucky enough to meet someone who noticed you in Greenest.