Collect 10 Loathsome Remnants from the twisted spirits in Kirin'Var Village's Chapel Yard and bring them to Custodian Dieworth.
The strange magical device resembles nothing you've ever seen before. It's certainly not of blood elf manufacture.
As you sense spirits moving closer to the building, the orb glows with a greater intensity, which fades as the spirits leave. There's no question that it plays a role in the corruption of the ghosts.
How it works remains a mystery. Perhaps Custodian Dieworth will have some insight if you can provide the remains of some of the spirits along with your observations.