Guild Wars players can expect the return of the infamous Mad King Thorn. This joker typically visits different areas of towns telling people what to do, rewarding those that listen and destroying those that don't. The two cities he will make appearances at are Lion's Arch and Kamadan, and you'll need to be around between October 26th and midnight October 31st to catch him.
Lineage II fans will see the "Trick or Transmutation" event for their Halloween celebration. This will involve a treasure hunt for some Alchemist's Chests, to create Philosopher's Stones and unlock rewards. Some of these rewards will reportedly be unique to this event, and if you're interested in trying your hand at the hunt, the event begins October 26th.
Finally, NCsoft is even infusing their unreleased MMO Tabula Rasa with Halloween madness. Those who have preordered the game will get to play a few days early, in the headstart promotion, and will be able to go on missions to earn special Halloween masks.
If you want to find out about the celebrations already going on in CoX check out our previous coverage, and a link to 1Up's article is provided below.