It's the end of another World of Warcraft expansion, and you know what that means: it's time to utterly wreck the power curve. Here's how to buy your own Corruptions in Battle for Azeroth.

World of Warcraft: Preserved Contaminant Guide

For those who are just joining us: Corruption effects, introduced in patch 8.3, can appear randomly on any newly acquired piece of gear in Battle for Azeroth zones. They're also guaranteed to show up on items you earn via the Visions of N'Zoth scenarios, and certain raid drops in Nya'lotha have predetermined unique Corruptions. Each Corruption effect conveys a set benefit, ranging from the extremely powerful (direct damage, a big whack of Leech rating, inflicting a powerful bleed) to the extremely underwhelming (Avoidance, Glimpse of Clarity).

Name

Effect

Corruption Increase

Avoidant

Your Avoidance is increased by 8/12/16% of your Haste.

+8/12/16

Deadly Momentum

Your critical hits have a chance to increase your Critical Strike by 31/41/72for 15 sec, stacking up to 5 times.

+15/20/35

Echoing Void

Your damaging abilities build the Echoing Void. Each time it builds, Echoing Void has a chance to collapse, dealing 0.40/0.60/1%of your Health as Shadow damage to all nearby enemies every 1 sec until no stacks remain.

+25/35/60

Expedient

Increases the amount of Haste you gain from all sources by 6/9/12%.

+10/15/20

Glimpse of Clarity

Your spells and abilities have a chance to grant you a Glimpse of Clarity, reducing the cooldown of your next spell cast by 3 sec.

+15

Gushing Wound***

Your damaging spells and abilities have a chance to cause your target to ooze blood, dealing damage over 7 sec.

+15

Honed Mind

Your spells and abilities have a chance to increase your Mastery by 392/523/915 for 10 sec.

+15/20/35

Ineffable Truth

Your spells and abilities have a chance to show you the Ineffable Truth, increasing the rate your cooldowns recover by 30/50% for 10 sec.

+12/30

Infinite Stars*

Your spells and abilities have a chance to strike a nearby enemy with an Infinite Star, dealing Arcane damage and increasing their damage taken from your Infinite Stars by 25%, stacking up to 10 times.

+20/50/75

Masterful

Increases the amount of Mastery you gain from all sources by 6/9/12%.

+10/15/20

Racing Pulse

Your spells and abilities have a chance to increase your Haste by 546/728/1275for 4 sec.

+15/20/35

Severe

Increases the amount of Critical Strike you gain from all sources by 6/9/12%.

+10/15/20

Siphoner

Increases Leech by 3/5/8%.

+10/15/20

Strikethrough

Increases the damage and healing you deal with Critical Strikes by 2/3/4%.

+10/15/20

Surging Vitality

Taking damage has a chance to increase your Versatility by 312/416/728 for 20 sec.

+15/20/35

Twilight Devastation**

Your attacks have a chance to trigger a beam of Twilight Devastation, dealing damage equal to 6/12/18% of your health to all enemies in front of you.

+25/50/75

Twisted Appendage*

Your attacks have a chance to spawn a tentacle which Mind Flays your target for Shadow damage every second for 10 sec.

+15/35/66

Versatile

Increases the amount of Versatility you gain from all sources by 6/9/12%.

+10/15/20

Void Ritual****

Gain Void Ritual, giving your spells and abilities a chance to increase all secondary stats by 14/34/64 every sec for 20 sec. This chance is increased if at least 2 nearby allies also have Void Ritual.

+15/35/66

*: The exact damage done by the effect scales based on the piece’s item level. It was previously determined by the user’s attack or spell power, but was hotfixed to keep players from feeling like they had to use low-level gear with beneficial Corruptions.
**: The Devastation beam has a 12-second internal cooldown and deals half damage to enemy players.
***: The amount of damage Gushing Wound does is roughly equal to 91% of your attack or spell power. Its damage is scheduled to be nerfed by 35% after the 5/26 server reset, to keep people from stacking it on every item and bleeding entire raid bosses out.
****: This is very common, and somewhat better than it looks. Your first item from an invasion cache is always a set of bracers with Rank 1 Void Ritual.

As a trade-off, the more Corruption you have and the stronger it is, the more detrimental effects accumulate on your character, and the more you start looking like you got caught in some kind of demonic oil spill. You can compensate for some of it by equipping and strengthening your cloak from Wrathion, as well as using the various azerite essences introduced in 8.3 like Breath of the Dying, but Corruption can accumulate a lot faster than your resistance to it ever will. You can purge Corruption from an item permanently, along with its beneficial effect, by having MOTHER purify it. This costs 5 Corrupted Mementos, which are obtained from the Visions of N'Zoth scenario.

Corruption

Negative Effect

1-19

Grasping Tendrils: Taking damage inflicts a short-duration snare.

20-39

Eye of Corruption: Your spells and abilities can spawn an untargetable eye that inflicts Shadow damage on you every 2 seconds while you remain in its target area. The size of the area increases as your Corruption level does, and the damage from the Eye inflicts a stacking debuff that makes the Eye’s damage hit harder. 

40-59

Grand Delusions: Taking damage may spawn a Thing from Beyond that pursues you for 8 seconds. It moves faster as your Corruption increases and deals high melee damage on contact.

60-79

Cascading Disaster: The Thing from Beyond’s melee damage also inflicts Grasping Tendrils and conjures the Eye of Corruption.

80+

Inevitable Doom: You take more damage and receive less healing. This is a debuff that starts at 5% and goes down by 1% for every additional point of Corruption beyond 80. You will also be glowing lethal red and be despised by every healer who sees you.

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Like a lot of other things about Battle for Azeroth, Corruption has turned gearing up for raiding into even more of a random numbers game than usual. In particular, the difference between great and mediocre DPS in Nya'lotha was largely down to your available Corruption effects. That changed abruptly on May 19th, however, as Blizzard introduced Preserved Contaminants. These items are sold by MOTHER in the Chamber of Heart in exchange for Echoes of Nya'lotha, and each one allows you to apply a specific Corruption effect, at a specific strength, to a previously uncorrupted piece of equipment. Shenanigans are about to ensue.

Blizzard has not taken the brakes quite all the way off the train, however. Each Preserved Contaminant costs 2,500 Echoes, and while the rate at which Echoes drop has been multiplied by 5, you're still not going to get more than about 2,500 of them per week from all available sources. This is designed as a steady weekly DPS gain, not a sudden power spike. Here's what you can do to farm Echoes: 

Source

Echoes Gained

Major Assault

625

Minor Assault

375

Raid Boss

75-125

Emissary Quest

250

Random Battleground Win

75-125

Rated Arena Match Win

75-125

Rated Battleground Win

175

Mythic+ Dungeon

15 x (Keystone Level)

Quest: Battle for Darkshore (Heroic)

375

Looking for Raid

125/wing

Weekly Mythic+ Cache

100 x (Keystone Level)

Weekly PVP Cache

875

MOTHER only sells a set number of Contaminants at a time, which will rotate twice a week at the same time the minor invasions switch over. Hence, at server reset on Tuesday and 7 PM on Friday nights, MOTHER's Contaminants stock will switch over. At time of writing, she's selling two rank 1 Contaminants (Ineffable Truth and Honed Mind), two Rank 2 (Strikethrough and Masterful), and two Rank 3 (Expedient and Twisted Appendage).

Another related change has made it easier to upgrade your Ashjra'kamas cloak to Rank 15. Several of those quests would require enough items obtained from clearing deeper parts of the Vision that you'd need to run the Visions scenario multiple times to get past a single step. Now, any given quest along the way can be completed in as little as a single run, which comes with a hefty boost to your Corruption Resistance.

In many past World of Warcraft expansions, Blizzard has directly nerfed raid encounters' damage and health, or provided grindable ways to directly increase endgame characters' health like the ring upgrades in Warlords of Draenor. This time, we've been given the option to choose exactly what kinds of horrible little Lovecraftian monsters we want to become. Call it progress, of a sort.

As we warm up for Shadowlands at the end of the year, we've also been dipping back into World of Warcraft. Check out some of the guides at our game hub:

My biggest problem with World of Warcraft's current endgame is that you'd think we'd get more out of avoiding N'Zoth's power, rather than trying to use it against him. It may be cool and all to level an entire herd of enemies with giant black pillars of destruction, but this doesn't seem like it could possibly end well. Share my apprehensions with me via our official Twitter, @PrimaGames.