At its heart, the event is all about traipsing through the nearest graveyard looking for enemies to dispose of as a particularly spooky plane of existence overlaps with the prime material plane (i.e., the place where the player characters live). There are also potions allowing players a chance at getting Night Revels rewards from any undead opponent killed anywhere in the game. You can also check out a video of the event just below if you’d like to see the monster-bashing event before you start in on participating.
Source: Official Site, YouTube. Thanks, DDOCentral.