A sneak peak of Sartok's Surprise, the upcoming Halloween event, has been posted on Vanguard Players. While it doesn't give a launch date, it does tell us that "three terrifying new undead raid encounters will be roaming the lands seeking out adventures both young and old." These terrifying monsters are under the control of the sinister necromancer Sartok, hence the event's name.
Any heroes able to best Sartok’s abominable creations will be rewarded with special appearance-altering costumes and magical masks. While adventurers rest between battles, they can complete special new quests to claim additional rewards such as new pets or more magical masks.
Keep checking Allakhazam and Vanguard Players for more information on Sartok's Surprise as it is released.