"How would our pursuit look like, my dear friend?" asked Dumbledore.
"Much like setting a bloodhound on a trail," Shin replied. "Perhaps it is because I have used my own blood so glibly for so long to perform magic, but my senses has become hypersensitive to the presence of life that has magic. All practitioners of blood-based magic seem to experience this sensitivity. My daughter can hear a magic's heartbeat, as it were, and the man I've told you about can perceive them through touch."
"Fascinating," said Dumbledore. "And you?"
"I can smell it."
"I assume soul wands and Horcruxes have a particular smell."
"They do."
"May ask what kind of smell?"
Shin stopped his pace. Dumbledore waited as he watched the moonlight playing across Shin's face.
"…Filth," Shin finally muttered, "decay; putrefaction; death; it doesn't matter whether the soul locked inside was that of a good person, bad person, or a young child—they all smell like rot to me."
The rest of their trek continued in grave silence.