Steal Acquire [Haunted Momento] Haunted Memento - Item - World of Warcraft
Once you obtain [Haunted Momento] you obviously have the buff and the spirit following you around.
then do this:
1. Relog (log out with the haunted momento on your person)
2. mail [Haunted Momento] to one of your alts
3. relog (after you mail the [Haunted Momento] buff and spirit go away)
4. When you log back in you have the buff and spirit again even without [Haunted Momento] in your inventory.
Haven't had time to see if this goes away upon entering a battleground or arena or if there is a limit of characters to replicate this on.
Enjoy your infinite buff/pet and trolllaxin!