MyCatPaws
An intersting twist would be if the missing people aren’t fully dead. The souls of the people are used to make the statues. Their souls are stuck inside each of them and their bodies are used to become the Material for tHe statues. The Cabin is probably a place that has been used by the mages From Ishid’s family (the aide of the second Prince) for them to transport or do experiments wIth slaves. They likely train snakes to Catch runaway slaves, Which is why the krokta was chasing Gab. There was likely a shield that hid the cabin from sight till now since the Cabin was old but the blood is fresh.
I speculate that the missing people were sacrificed and that's the source for the artficial dark mana that's being used in the statues. And the cabins maybe situated all throughout the kingdom, specifically in the dukedoms of all the dukes in the Crown Prince's faction. Elise and the Temple of Light will probably pin this on the Crown Prince's faction and Duke Emsworth, saying that they're producing dark mana to counter the Temple of Light.
The temple of light used the missing people to extract their souls. While the missing people were inside the sacrificial seal, they will feel agony, deep hatred, revenge, and all negative emotions that a human can feel. Those accumulated negative emotions will converted to be a dark mana and will be fed in statues to become artificial source dark mana. The cabin was not found easily because it was covered in illusion magic. And the merchant who found the cabin is Gil.