Locate Beren's Peril, then kill 6 Ravenclaw Drudgers and 6 Ravenclaw Guardians, then return to Shadow Priest Allister at the Sepulcher.
I have received reports that a group of undead are holing up to prepare for an attack against us. Armed with this information, we can turn the tables and attack them first, nipping their little plan in the bud.
Unfortunately, my information is spotty, at best. They are reported to be hiding in a location known as Beren's Peril. The exact location is unknown, but it appears to be a cave in the hills, near a pocket of Dalaran wizards.
I trust your resourcefulness. Find them, and put them down.