World of Warcraft. what are those shady untargetable creatures floating around in Ironforge?

It's from haunted memento. I've got one. They were part of an event preWOTLK from killing scourge. If you have one in your bags, you'll have some buff, forget what it says...think haunted or something of that sort, but a ghost will follow you around. They're a little slow on following, but they don't disappear if you get too far like with non-combat pets.