The Wild Hunt

Originally started as a way to find and punish those mortals who insulted and assaulted the Changed, or fae as they were known on Old Earth, the hunt kept to its times and its purpose for thousands of years. After the Changed returned to Underhill to live, they kept the tradition alive. Since they didn't have humans hunting them, warding against them, or otherwise trying to involve themselves with the fae, the Hunt had new quarry. Finding the descendants of the Changed themselves. For all the years they lived on Old Earth, the Changed took human mates and left human offspring behind. Hundreds and thousands of years later, some of those offspring's offspring are still around. And show unique genetic markers. And during the seasons when no descendants could be found? Well, tradition is tradition, and there's always some hapless fool who can be tricked into bearing the mark of the hind.