This is another yearly recurring event that will be included for Reaper of Souls/Adventure Mode by Blizzard for Diablo III. Note, this will only be available on January every year.
So far, after testing it on PTR, here is a summary of it:
There will be specific Achievements on your Achievements list for doing things such as killing Uniques that only spawn within the event, starting the entire event with a level 1 character, etc.
Limited Transmogs of items
Old items will drop (but with crappy stats) such as Plates, Quarter Staffs, etc. for those who have played Diablo I
The graphics and slight stutter makes it feel like a retro 16-bit game
the levels are a lot more straightforward than the actual Diablo I's by comparison
You will have to run multiple times to complete the achievements
Certain achievements give you Portrait, Banner patterns, and pets
So that's the summary from my testing. Nice addition but I think they could do better with the PTR patch, it's too focused on this limited-time event.
This post has been edited by Kevmeister: Nov 9 2016, 07:45 PM
It's not. It causes your character to stay-still, similarly in the state of being Stunned to unleash the ring of fire (similar to Diablo II's Diablo Ring of Fire attack), and procs randomly.
So halfway trying to teleport to town and this proc, you will be interrupted. Damage-wise, so-so, secondary effect is useless in a competitive scenario.