Sometimes the event will start from the first wandering skeleton, sometimes it will not start even after killing them all. Generally the event is bugged and you will get 0-12 of the items you need. Other times you will be unable to hit them. In the event that the event gets bugged, you will have to delete the quest and try again or wait 24 hours. This event was never fully tested even after it went live.
go to the Bloody Battlegrounds and engage the non-aggro human spirits (if you evil) that now populate the area. Kill one at a time, or more if you can survive it. Each one that you kill will leave a spirit behind. You then use the phylactery on the spirit.