The Moai Head

You stumble across something that feels *very* out of place. Before you, an enormous stony head emerges from a large wall segment that does not shift and change like the rest of this area. The head's mouth is wide open, and it reveals large intimidating teeth stained red with blood. The surface of the statue is riddled with pictographs that seem to indicate people throwing themselves into the mouth of this head and being devoured. Why would anyone do that?