- The Ethereal Soul-trader
The Soul-trader is a summonable NPC vendor -- you'll get currency for killing things while he's around, and you can trade that in for extra items, including special food and drink, an energy ball to play catch with, and even the Ethereal's wardrobe, wearable on your own character.
- The Path of Illidan
The Path of Illidan loot card will let you leave green, glowing footprints whereever you go.
- D.I.S.C.O. party!
The DISCO card will let you summon a party, including disco ball, and ingame music for your friends to dance to.
- Gaining currency
The Ethereal Soul-trade will give you currency for each mob you kill with him summoned -- apparently the payoff is pretty flashy.