The green stuff is slime. Looks a lot like the slime that was around the cemetery, but greener. You aren’t sure what that means.
It also looks like there’s something inside the slime. Something about as big as a human. If they were crouching down, anyways. And with a number of priests gone missing… well, it’s not impossible you’ve found one of them.
But you also don’t want to touch that slime if you can help it. It doesn’t have an aura, exactly, but the odd sense of stagnancy feels a bit stronger when you focus on it. Not to mention there seem to be sharp plants growing through it. Plants you don’t recognize.
It’ll be hard to go very far from here, though. Going away with the artifacts would just cover the slime in water, which might not go so well for whatever’s inside it. You suppose you could leave the objects here, but you’d need to protect them somehow. And you’re getting ahead of yourself if you do that without any plan for how it would help you, anyways.
Well. Maybe there’s something you can do with what’s at hand. You pull a plank loose from the wall you knocked over. It’s wet, but it should be good enough for poking and prodding without touching the slime yourself. You reach out towards the mass in the center with the plank, and see what you hit.