Diablo's 20th Anniversary

This is probably going to be a Feat of Strength commemorating Diablo's 20th anniversary, and it includes some interesting items that will be available during this event such as
- [item=143628]
- [item=143543]
- [item=143326]
- [item=142544]
- [item=142543]
- [item=142542]

Most of them are actually items in the Diablo universe as well.

In order to get this Feat of Strength you need to learn the toy [item=143543] dropped by [npc=116034] in the Cow Level, which you can access by killing a [npc=116041] and entering the portal he spawns when killed.

To get this achievment you have to loot and use [item=143543] from [npc=116034]

[npc=116034] is found by finding a [npc=116041] around the world (I found one just outside of Thunder Totem), killing it and venturing through the portal that is left by his corpse!

When you kill the king you get various charms that are usable during the Diablo anniversary and also get the toy [item=143543] which gives you the achievement Diablo's 20th Anniversary

Do not throw these scrolls away or waste them as you can combine 10 [item=142543] with a [item=143628] to create [item=142542]

The event starts on the 3rd of January (00:00AM), 2017 and should run until the 11th of January 2017.
There are still no certain facts regarding how to obtain any of the items. Legion Alpha and datamining shows Treasure Goblin & [npc=89407] mobs within this Scenario that will drop [item=122291] which will most likely be a currency for the [item=143326] (which might both be rare drops and a vendor item). [item=143326] might be the currency required in obtaining the [item=143543].

Another speculation on obtaining Diablo's 20th Anniversary (or at least a specific Achievement related to it) is that you are required to obtain the [item=143543]. This achievement will most definitely be a limited-time Feat of Strength, similar to Boldly, You Sought the Power of Ragnaros, but without any evidence of a reward (Pet or Mount). However, these are still only theories, considering that Blizzard have yet to release any statements regarding the event.

04.01.2017 Edit: It seems Treasure Goblins spawn after the completion of a dungeon (which happened for us), and upon killing it you can enter the portal and kill the Cow boss which will drop the [item=143543]. However they can spawn outdoors within the Broken Isles as well. Do note that they can bug out (which happened for us) and evade the attacks and use the Escape Portal. Completing/using this (toy) will reward you with Diablo's 20th Anniversary, as was my speculation above.