Forest

Well, now. The smell of decay is interesting, and something Mateo's olfactory organs are good at picking up. The hoofprints are also interesting, though Mateo isn't good with horses. He suspects it's a herd of unicorns or centaur, though, as other horses aren't woodland species. But it could easily be some vast, multi-limbed monster that happens to be hoofed. And then there's the light, which is also interesting. Mateo tries to see if the equine creature(s) or the smell are heading towards the light. Maybe it'll be easy, and all the signs are part of one larger phenomena.

Mateo does hope it isn't unicorns, though; they're inherently divine, and are therefore capable of killing a vampire without using the methods other creatures have to resort to.