The first thing Seth would have noticed upon poking his little figurine head out of the corpses clothes was the thick, almost oppressive metallic stench of blood. There was so much iron in the air that a TSA agent would be trying to frisk it.
Now, You would think that is a stench that he would have been used to by now, with how much he has personally killed and the waves of beasts he has cut down, and you would be right, for the most part.
One must understand that the overwhelming nature of this stench was not its origin, but instead a matter of pure scale. It was like the difference between smelling a single turd in front of you versus an entire football field of faeces piled as high as the pyramids.