For all players. There could be different hunts for each level. Beginning/Apprentice, Medium/Adept and Hard/Master. And of course we can all help each other. We could find awesome loot from all the Spiral areas, dungeons, the grounds, where ever KI wants to put things. The loot could include Awesome pets (some really rare), Furniture, gardening, clothing, and weapons, wands, decks, etc.
For example, I am a legendary and I choose the master scavenger hunt, I can bring in my lower lever friends to help me. Maybe they choose the adept hunt (because they are not in Dragonspyre or Celestia yet). We can all help each other and the loot drops will differ. The harder the scavenger hunt, the rarer the drops. And the people that help the scavenger hunters don't even have to be Scavenger Hunts, then they will get the regular game drops.
The scavenger hunters can choose the levels over and over, just like with the three towers in the Halloween Quest.