In the marketplace, you talk to Taj, the egg collector. Then you run around the marketplace collecting egg within a limited time.
Last year I managed to get ultimate aura consistently.
Anyways, here are some tips I've heard so far. I'll let you guys know how I make out this year.
First off, you only get ONE blessing, but 10 tokens. So save that blessing for when you get a high enough aura you want to use.
I hear that using the blessing when you have ultimate aura still only gives crappy +2 store potions, but if you use the blessing on major aura, one level lower: you can get xp pots and other good stuff. I probably will still test this out a bit myself, but I only have 9 blessings to work with!!
I hear this year, a ultimate aura without a blessing is giving out +3 unbound tomes. Happy hunting!!