NCsoft checks in with their Trick or Treat GM Event for Lineage 2. Kicking off today and running through October 28th, the event requires you to go hunting between 9:00 am and 6:00 pm Pacific time. If you see an elpy appear next to you, you'll have 20 seconds to /say or /shout "trick or treat."
If successful, a GM will transform you into a werewolf and teleport you to a special instance featuring a ton of loot-bearing elpies waiting to fall on your blade (or your claws). You'll be hauling in a ton of goodies, so you might want to consider clearing your inventory ahead of time. Read up on all the details at the official Lineage 2 website.