The Darkening of Tristram is a special Anniversary event that becomes available in Diablo III every January. The first time the event was released was on December 31, 2017. It was the 20 year anniversary of Diablo I.
There are several Achievements that players can earn in The Darkening of Tristram event. If you don’t manage to complete everything all at once – don’t worry! The Achievements you earn one year “stick”, and you won’t have to re-earn them every year. You can pick up where you left off.
Adventuring Hero: Kill one unique monster from the Labyrinth.
I killed Rotfeast the Hungry.
The Dark Passage: Visit the Dark Passage.
The Chamber of Bone: Visit the Chamber of Bone.
The Halls of the Blind: Visit the Halls of the Blind.
Champion of the Townsfolk: Kill 20 unique monsters from the Labyrinth.
I killed: Nightwing the Cold, Goldblight the Flame, Viletouch, Snotspill, Foulwing, Gharbad the Weak, Deathshade Fleshmaul, Bloodgutter, Bloodskin Darkbow, Zhar the Mad, The Vizier, Breakspine, Firewound the Grim, Rustweaver, Steelskul the Hunter, Warlord of Blood, Sir Gorash, Madeye the Dead, Blacklash the Burning, Fangspeir, Blackjade, Red Vex, Rotfeast the Hungry
Thank Goodness You’ve Returned!: Kill all 4 bosses in The Darkening of Tristram event.
Players who completed that Achievement earn two banner rewards: a Banner Sigil and a Banner Accent.
I Sense A Soul in Search of Answers: Collect all the Cultist Pages from the precursor event.
Players who complete this Achievement receive a Portrait Frame reward.
Pssst… Over Here…: Acquire Wirt’s Leg in The Darkening of Tristram event.
Players who complete this Achievement receive a special Transmog… that looks like Wirt’s leg.
An Eerie Red Glow Blurs Your Vision: Kill the Dark Lord in a solo game starting with a Level 1 character in The Darkening of Tristram event.
Players who complete this Achievement receive a Pet Award. It is the Butcher Pet.
Protector of Tristram: Kill all unique monsters from the Labyrinth.
Players who complete this Achievement get a receive a Portrait Frame.