After finding Adventurer’s Remains or Adventurer’s Spirit in one of the locations listed below, you will have to team up with another healer of any class to start the ritual. This will summon a mob, which will drop a rune for every player involved when defeated. However, the mob will despawn for some time after somebody finishes it, meaning it’s harder to complete in popular zones.
Durotar
Near a tree in Kolkar Crag (canyon inhabited by centaurs south of Valley of Trials), /way 48.0 79.6.
Mulgore
On an overlook at /way 60.4 33.6; you have to go through the Venture Co. Mine to reach it.