Ah!! We get a little more information here on the arm. It belongs to a statue someplace. Now I’m expecting they are reassembling a statue someplace, maybe to summon the being it represents? No spoilers here, I’m reading this as you do, so this is just speculation on my part.
The villain says he hoped to draw Enemus here, but was he actually expecting Enemus, or just an agent of the Penumbra? This appears to be their first meeting, so I’d be surprised if he had any animous specifically against Enemus himself.