The very first one was used to help assemble the Bone Plague Army for the Battle of Sunsplint Fields.
Screams shatter the peace of the area as you are moving through it. You tumble to the ground bucking and shifting under you. The minor tremors you have felt over the last several minutes seem to have gotten much stronger. The worst of it subsides slowly. The ground vibrates without pause for nearly a full minute after the initial violent shock. Suddenly, the ground erupts, mud covered white bones crawling from wounds in the earth like open graves! The soil vomits up skeletons of multiple humanoids and creatures big and small alike.
This feature is part of Lich Lord’s Anger Manifest.