Courtesy of the new 1.37 GB patch, the event has spawned goose eggs all over the place. If players find and turn these in to their creepy black spirit, they can then unlock an additional quest. Presumably, there are rewards sprinkled in there as well. The event starts today and will run through April 19th.
There’s a little more to the patch than that, of course. The team has made some improvements to the in-game marketplace, fixed dueling mechanics to make it a bit safer from griefing, and allowed housing items to be placed on wall shelves. Oh, and now there are watermarks on all of your screenshots because someone out there must have put that in the suggestion box. Was it you, George? We totally know it was. Thanks a LOT.
Source: Patch notes