Here’s a very quick summary of the important changes, with links to additional infos. Diablo 3 Patch 2.1.2 Survival Guide:
General Gameplay:

Class and skill changes:
Items


Monsters






Click through for much more info on the coming feature changes in Patch 2.1.2, plus a reminder that Season Two and all of its new features are not coming with the Patch, and won’t be here until a week or two after Season One ends on February 3.
Season Two =/= Patch 2.1.2
Just the Patch is coming this week. Season 1 ending and Season 2 starting doesn’t happen until February 3rd at the soonest.
Also note that putting up a content patch mid-season is *not* how Blizzard wants to do things going forward. This time was out of order, largely due to the holiday vacation. In the future, Blizzard plans to end a season, launch a new patch, give even non-PTR players a few days to experiment, and then start the next season.
Patch Notes Preview
Patch 2.1.2 was on the PTR for a couple of months, and after a lot of early tweaks and changes, it was content-complete on the PTR back before Xmas, so the live version of Patch 2.1.2 is going to be almost identical to what players were testing. Which means the last Patch Notes tell almost everything coming in the patch. You can see them, from December 9th, here.
Conduit Pylons
Everyone’s favorite shrine in the current game will be no one’s favorite in Patch 2.1.2. The super powerful yellow lightning death shrine still looks and functions the same, but the damage is *much* lower in Patch 2.1.2, and based on your weapon damage, rather than scaling by the game difficulty.How low? Much too low, in the opinion of most PTR players, since the shrine isn’t fun anymore, with not enough power to even destroy trash mobs, much less Elites. (And it does almost nothing to Guardians.) For example, my well-geared PTR Demon Hunter got crits of around 13m from a Conduit Pylon, while her normal Multishot attacks scored crits of 50-60 million per shot. (Unbuffed.)
The nerf was not a real surprise, as players had taken to referring to the highest levels of Greater Rifts as “Conduit Rifts” since the best times were being made or broken entirely by frequency of Conduit Pylons, and smart players in parties were sending someone rushing back to the Conduit when they were nearly done, hitting the Conduit when the rest of the party reached about 98%, so they’d zap down the Guardian in an instant.
Blizzard didn’t want one shrine having such an out-sized impact on high end play, and they’d repeatedly talked about needing some kind of Conduit nerf. Unfortunately they took it much too far, and in Patch 2.1.2 the Conduit Pylon is almost useless, especially on higher difficulty levels. Fortunately, it shouldn’t be forever. A dev told me personally that the Conduit Pylon is set for a buff… Unfortunately that’s not going to happen until the next patch after v2.1.2 (or possibly in a hotfix).
Unless they can hotfix that in very soon, we’re doomed to endure days of “Y R U nerf Condit!!?1?” posts from people who haven’t been following the PTR news. I’ll be sure to news about them, so you all can suffer with me. Teamwork!
Treasure Goblins
There are four new types of Treasure Goblins. Screenshots and details about them can be seen in a recent article.




Greater Rift Changes
Normal Rifts and especially Greater Rifts have been improved in a quality of life way. The density is much increased (especially in GRifts) and there are more varied types of monsters on each level. The maps are also bigger and better, with very few dead ends and better shapes and layouts.Refer to our recent article about Rift testing on the PTR for full details and screens.
Ancient Items
We’ve written a lot about these already, so refer to our huge article with 100+ screenshots for full details. The DiabloWiki.net Ancient Items article is also up to date and extensive.
Ancient does not affect Legendary Affixes or Set Bonuses in any way; it’s just a buff to some of the affixes on the item.
Ancient spawns on about 1.5% of legendary items dropped on Torment 1, scaling up to around 10% on Torment 6. It seems to be around 10% for all crafted and gambled legendary items, regardless of difficulty level.
Your first priority when Patch 2.1.2 goes live should be to upgrade to an Ancient weapon. You might gamble or find one, but the best way to get one quickly is by crafting. This is something of a loop hole, but one very worth exploiting by players who want a big DPS buff, and who are not stuck with a Legendary Item they *require* for their build to work.
Any Ancient Weapon with a decent roll will be a huge damage upgrade. Ancient Armor can potentially be much better, with higher possible numbers to mainstat, vitality, ResAll, and more. But finding pieces with the ideal combination of affixes is very hard. Jewelry is almost irrelevant with Ancient, since all the best jewelry affixes (Crit Chance, Crit Damage, IAS, socket, Cooldown Reduction, and +Elemental Damage) are unaffected by Ancient. The only useful affixes on jewelry that get a boost from Ancient are mainstat.
Long term, players will replace some of their gear with Ancient items, but this will take longer the better your kit is. Playing on the PTR during the insane +2000% legendary drop rate buff, I saw hundreds of legendary items per game, with about 10% of those Ancient, and my DH was only wearing ancient in 7 or 8 slots. (Screens of all those equipped items can be seen in our big Ancient Items writeup.) Playing the real game with a real drop rate, ancient armor/jewelry will seldom be an upgrade over your current gear… but Ancient adds some excitement to every legendary weapon ID, and you’ve always got the chance to roll very lucky on Ancient Armor and step into a nice upgrade.
Conclusion
There’s a ton more to write about the changes in Patch 2.1.2, so check the linked articles for more detail, or pose your specific questions in the comments. The PTR ran so long that many regular readers did extensive testing, and many of us will be happy to answer questions. Or at least speculate with some authority, for the benefit of non-PTR players.
I’m personally ready for the Patch to go live, and looking forward to some Legendary Weapon crafting right off the bat, before I leap into Greater Rifts and see if the density changes are the same as they were on the PTR. Last week playing on Live after the PTR shut down, I was annoyed at how empty the Grifts felt, and how lame were some of the maps and layouts. That aspect of Rifts is definitely very improved in Patch 2.1.2, in a very “quality of life” sort of way. Embrace the upgrades.