Diablo 3 is opening up the anniversary event, The Darkening of Tristram, once more. The event returns as a tribute to the Diablo franchise’s origins and as another opportunity to defeat a bunch of cultists, face the Dark Lord, and walk away with some loot.
Starting tomorrow, December 31st, at 4:00 p.m. Pacific, cultists will appear and you can start your journey. The cultists are starting trouble and sanctuary and they are ripe for hunting down in Adventure Mode. You'll have plenty of cultists to take down, and if you've played through the event before, you'll know what to expect. Ultimately, as you take down more cultists, you'll find clues that will lead you to a special portal. When you step inside that portal, you'll uncover Tristram's past and what happened to the town.
The portal will open up on January 3rd, and the event itself fully ends on January 31st. You have a few days to get settled and to hunt down your cultists and find those clues. Then get ready to enter the portal and explore the dungeon, discover the history of the town, encounter familiar items and enemies from Sanctuary's past in the Diablo 3 engine, and an encounter with the dark lord himself under the catacombs.
Of course it's Diablo, so there is loot. In the anniversary event, you'll potentially get things like unique transmog effects, achievements, pets, and portraits. There are some rewards that are easier to find and others that are designed to be challenging. If you're a veteran of this event, you're probably ready to get in there, knock a few cultists around and get off and running to collect your spoils.
The official event announcement has full details on what to expect.